HAWAII  AGRICULTURAL  EXPERIMENT  STATION 

HONOLULU,  HAWAII 

Under  the  supervision  of  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


BULLETIN  No.  56 


CARBOHYDRATE  METABOLISM  AND 

ITS  RELATION  TO  GROWTH  IN  THE 

EDIBLE  CANNA 


BY 


J.  C.  RIPPERTON,  Chemist 


Issued  May,  1927 


m# 


:*  i 

UNITED  STATES  ^*^ 

GOVERNMENT  PRINTING  OFFICE 
WASHINGTON 

1927 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU 

[Under  the  supervision  of  the  Office  of  Experiment  Stations,  United  States  Department  of  Agriculture] 

E.  W.  Allen,  Chief,  Office  of  Experiment  Stations. 
Walter  H.  Evans,  Chief,   Division  of  Insular  Stations,  Office  of  Experiment 

Stations. 


STATION  STAFF 

J.  M.  Westgate,  Director. 

W.  T.  Pope,  Horticulturist. 

H.  L.  Chung,  Agronomist. 

J.  C.  Ripperton,  Chemist. 

R.  A.  Gofp,  Extension  Agent  for  the  Island  of  Hawaii,  Hilo,  Hawaii. 

Mabel  Greene,  Boys'  and  Girls'  Club  Leader. 

H.  F.  Willey,  Superintendent,  Haleakala  Demonstration  Farm,  Makawao,  Maui, 

Hawaii. 
R.  K.  Lum,  Junior  Tropical  Agronomist. l 

*  Appointed  Nov  1,1925 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 
HONOLULU,  HAWAII 

Under  the  supervision  or  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


BULLETIN  NO.  56 


Washington,  D.  C.  May,  1927 


CARBOHYDRATE     METABOLISM    AND    ITS     RELA- 
TION TO  GROWTH  IN  THE  EDIBLE  CANNA 

By  J.  C.  Ripperton,  Chemist 


CONTENTS 


Page 

Habit  of  growth  of  the  edible  eanna 1 

Methods  of  investigation 5 

Carbohydrate  metabolism .__        11 

Cryoscopic  measurements  and  osmotic  pres- 
sure of  the  plant  juices 30 


Page 

Discussion  of  results 32 

Summary.-.. 33 

Literature  cited 34 


The  potential  importance  of  edible  canna  (Carina  edulis)  as  a  com- 
mercial source  of  starch  has  led  to  various  experiments  both  at  the 
central  station  in  Honolulu  and  at  Waimea,  Hawaii.  Although  the 
plant  is  well  known  botanically,  and  has  been  grown  in  Queensland, 
Australia,  for  many  years  for  starch,  the  available  literature  gives  no 
information  regarding  its  production  on  a  field  scale.  Field  methods 
of  study  devised  by  the  station  have  given  considerable  data  on  the 
growth  of  the  plant.  Laboratory  studies  of  the  carbohydrate  metab- 
olism of  the  plant  have  been  made  to  learn  the  significance  of  the 
field  results. 

HABIT  OF  GROWTH  OF  THE  EDIBLE  CANNA 

The  edible  canna  belongs  to  the  same  genus  as  the  familiar  flower- 
ing variety,  and  resembles  it  both  in  appearance  and  manner  of 
growth.  Starting  with  the  rootstock  and  the  original  stem,  growth 
takes  place  through  the  development  of  axillary  buds  growing  from 
the  nodes  of  the  rootstock.  Growth  within  the  hill  is  rapid  when 
conditions  are  favorable.  Development  of  the  bud  follows  closely 
development  of  the  parent,  so  that  in  a  vigorous  hill  as  many  as  10 
plants,1  representing  three  to  five  generations  (fig.  1),  maybe  growing 
simultaneously.  As  the  plant  reaches  maturity,  first  the  leaves  and 
then  the  stem  shrivel,  and  the  rootstock  becomes  dormant,  while  new 
growth  continues  through  the  developing  buds. 

1  The  term  "  plant "  is  used  to  denote  a  single  rootstock  and  its  attached  stem. 

35973—27 1  1 


BULLETIN    56,    HAWAII   EXPERIMENT  STATION 


The  storage  organ  or  lower  part  of  the  plant  is  essentially  a  root- 
stock,  or  part  of  the  stem  in  which  starch  is  stored,  and  morphologi- 
cally it  is  an  integral  part  of  the  stem.  In  some  of  the  types  of  slender 
rootstock  it  is  difficult  to  determine  just  where  the  rootstock  ends 
and  the  stem  proper  begins. 

Under  normal  conditions  the  new  rootstocks  attain  very  consider- 
able size  with  energy  supplied  by  the  parent  plant,  their  own  stems 
remaining  entirely  undeveloped.  (Figs.  1 ,  3, 4, 5, 6,  and  7  )  When  vig- 
orous growth  of  the  meristem 
decreases,  the  internodes  at 
the  apex  shorten  very  rap- 
idly, and  the  stem  develops. 
Under  optimum  conditions, 
the  rootstock  continues  to 
increase  in  size  for  some  time, 
as  is  shown  by  the  large,  fresh 
cracks  on  its  surface.  In- 
crease in  size,  however,  may 
be  the  result  of  cell  elongation 
rather  than  of  cell  growth. 
The  potency  of  the  parent 
stem  is  strikingly  shown  by 
the  fact  that  when  all  the  ma- 
ture top  is  removed  the  hill 
produces  extremely  stunted 
rootstocks.     (Fig.  8.) 

The  first  generation  root- 
stocks  are  always  small  and 
cylindrical  in  type;  the  sec- 
ond, and  sometimes  the  third 
generation,  termed  the  inter- 
mediate type,  have  a  definite 
tapering  shape.  They  grow 
below  the  surface  of  the 
ground,  starting  with  a  small 
attachment  to  the  parent, 
and  increase  in  diameter  to  a 
definite  bulge  approaching 
the  apex.  The  third  and 
fourth  generations,  under 
ordinary  cultural  methods, 
grow  at  or  near  the  surface 
of  the  ground,  starting  with  a 
large  attachment  to  the  par- 
ent. They  are  oval  to  spher- 
ical and  largely  develop  above 
the  surface  of  the  ground. 
(Fig.  3.)  Subsequent  gener- 
ations are  of  thissame 
general  surface  type. 
The  characteristic  shapes  (fig.  9)  may  be  attributed  largely  to  the 
number  of  antecedent  stems  upon  which  the  developing  rootstock 
has  to  draw.  The  first  generation  has  none  The  second  generation, 
which  closely  follows  the  first,  receives  little  plant  food  from  the  par- 


s  \\ 

\  V  i 

f        / 

I  H 

KB?*  ' 

Fig.  1.— A  hill  of  canna,  6  months  old,  at  its  maximum 
growing  stage.  The  stems  of  the  first  three  generations 
have  bloomed  and  are  functioning  at  their  maximum 
in  producing  sugars  for  the  stoiage  of  starch  and  for  the 
production  of  new  growth.  Note  the  large,  vigorous 
new  rootstocks 


CARBOHYDRATE  METABOLISM   AND  GROWTH  JX  EDIBLE  CANNA 


ent  at  first,  but  increases  in  diameter,  assuming  a  tapering  shape,  as 
the  quantity  of  food  received  increases.  The  surface  type,  which 
has  two  or  more  stems  on  which  to  draw,  starts  with  a  large  attach- 
ment to  the  parent  and  develops  an  oval  shape. 

Buds  are  produced  in  the  axils  of  the  scales  of  the  rootstock.  They 
are  sometimes  produced  in  profusion  on  the  cylindrical  type  of  root- 
stock,  but  most  of 
them  remain  dormant. 
Ordinarily  three  buds 
develop  on  rootstocks 
of  the  intermediate 
type,  being  attached  at 
intervals  from  near  the 
base  to  the  apical  part 
of  the  mature  root- 
stock.  Usually  only 
two  vigorous  buds 
grow  on  rootstocks  of 
the  surface  or  oval 
type,  and  they  are  at- 
tached near  the  apex. 
A  number  of  other 
buds,  termed  "top 
buds,"  which  are  very 
small  and  dormant, 
grow  at  the  very  short 
nodes  near  the  extreme 
apex  of  the  rootstock. 
(Fig.  10.)  Normally, 
these  do  not  develop, 
although  some  of  them 
may  grow  when  the 
rootstock  is  used  for 
seed. 

The  vigor  of  the  de- 
veloping bud  seems  to 
depend  upon  the  age  of 
the  parent  rootstock. 
A  bud  has  maximum 
vigor  if  it  starts  to  grow 
while  the  parent  is 
young  and  rapidly  de- 
veloping in  the  region 
of  bud  attachment. 
Growth  is  stunted, 
however,  and  the  size 
of  the  rootstock  ulti- 
mately greatly  de- 
ceases, \i  bud  development  is  retarded  until  the  parent  is  old  (fig.  8) ; 
hence,  the  edible  canna  requires  uniform  growing  conditions  to  make 
the  best  growth. 

Fields  of  canna  failing  to  send  out  much  new  growth  under  adverse 
conditions  may  produce  new  stems  in  profusion  with  the  return  of 


Fig.  2.— Longitudinal  section  of  an  intermediate  type  of  rootstock. 
A  is  the  first  node  of  the  stem;  B  is  the  apex  of  the  rootstock. 
The  characteristic  parallelism  of  the  vascular  bundles  in  the  stem 
differentiates  it  from  the  rootstock  proper 


BULLETIN    56,    HAWAII   EXPERIMENT    STATION 


favorable  conditions,  but  the  newly  formed  rootstocks  are  very  much 
undersize.  Grouping  the  hill  according  to  generations  shows  that 
the  new  growth  is  the  result  of  bud  development  on  all  the  generations. 
The  stunted  growth  is  termed  " secondary"  in  contrast  with  the 
vigorous  "primary",  growth  starting  while  the  parent  rootstock  is 
young.      (Figs.  11  and  12.) 

A  number  of  more  or  less  distinct  stages  occur  during  the  growth 
of  a  hill  of  canna.  The  first  stage  covers  the  establishment  of  the 
plant,  which  often  requires  as  long  as  three  months,  during  which  the 

first  two  generations 
develop.  The  root- 
stocks  lie  almost  en- 
tirely beneath  the  sur- 
face of  the  ground  and 
usually  are  small  and 
comparatively  low  in 
starch  content.  The 
second  stage  is  one  of 
rapid  development  of 
new  rootstocks  (fig.  4) , 
the  third,  fourth,  and 
fifth  generations  devel- 
oping in  quick  succes- 
sion. These  are  of  the 
oval-surface  type  and 
usually  are  large. 
After  these  generations 
h  a  v  e  developed  the 
new  growth  generally 
declines  in  vigor,  and 
the  rootstocks  decrease 
in  size.  The  original 
stem  dies,  and  the 
stems  of  subsequent 
generations  become 
less  vigorous.  With 
the  decline  in  vigor  of 
the  primary  growth,  the 
secondary  growth  be- 
gins, producing  smaller  rootstocks.  The  new  growth  thenceforth 
continues  to  produce  stems  of  diminishing  vigor  and  rootstocks 
decreasing  in  size  until  they  ultimately  become  undesirable  for  starch 
making. 

These  stages  of  growth  are  not  so  apparent  at  Waimea,  Hawaii, 
where  the  plant  seems  to  be  perfectly  adapted  to  both  soil  and 
climatic  conditions.  One  or  more  "lines"  in  the  hill  may  continue 
to  produce  large  primary  growth  for  an  indefinite  number  of  genera- 
tions notwithstanding  the  gradual  decrease  in  the  average  weight  of 
the  new  rootstocks  in  the  later  stages  of  growth. 


Fig.  3.— A  close-up  view  of  the  base  of  a  hill  4  months  old.  As  is 
characteristic  of  the  canna  plant,  the  newest  growth  is  mostly  on 
top  of  the  ground 


CARBOHYDRATE   METABOLISM   AND  GROWTH   IX   EDIBLE  CANNA  5 

METHODS    OF    INVESTIGATION 

FIELD   METHODS 

Two  general  methods  were  devised  for  continuous  study  of  the 
growth  of  edible  canna. 

In  the  first  method,  the  different  generations  of  the  rootstock  were 
studied,  tracing  the  progressive  growth  of  the  hill  from  the  original 
seed  rootstock.  The  hill  was  carefully  dug  and  the  individual 
plants  were  separated  and  grouped  according  to  successive  genera- 
tions, beginning  with  the  plant  developing  from  the  original  seed 
rootstock  as  the  first  generation.  Notes  were  then  made  of  the 
number,  kind,  and  size  of  the  rootstocks  of    each  generation,  the 


Fig.  4.— Top  view  of  a  hi!l  ol  canna  during  its  optimum  growing  stage  (4  months  old).  The  seven 
large  spike  rootstocks,  all  of  the  fourth  generation,  were  supported  by  nine  vigorous  stems.  Note 
the  profusion  of  smaller  secondary  "spikes  "  developing  in  the  center  of  the  hill 


stage  of  maturity  of  stems,  and  the  amount  of  both  primary  and 
secondary  growth. 

In  the  second  method,  the  classification  of  rootstocks  was  studied, 
the  lot  from  each  hill  being  grouped  as  dormant,  mature,  and  imma- 
ture. 

The  procedure  followed  was  to  dig  the  hill  of  canna  and  group 
the  different  plants  in  the  hill  according  to  the  stage  of  maturity 
of  their  stems.  Group  1,  dormant  stage,  composed  plants  on  which 
the  leaves  had  died  and  the  stem  had  partly  or  wholly  shriveled. 
This  group  appears  when  the  hill  is  8  to  12  months  old.  Group  2, 
mature  stage,  comprised  plants  whose  new  growth  within  the  stem 
had  ceased,  and,  in  case  of  the  older  members,  the  lower  leaves  had 
shriveled.  Group  3,  immature  stage,  comprised  plants  the  stems  of 
which  had  not  attained  their  maximum  growth.  Group  3  was  sub- 
divided into  two   lots   (a)  plants  with  stems  developing,  comprising 


6 


BULLETIN    56,   HAWAII   EXPERIMENT   STATION 


the  older  members  of  the  group  including  developing  stems  with  more 
than  one  leaf,  and  (b)  plants  with  stem  undeveloped,  composed 
chiefly  of  "spike"  rootstocks. 

LABORATORY    METHODS 

Determination  was  made  of  the  reducing  and  nonreducing  sugars 

in  the  sap  of  the  plant.     Immediately  after  the  plant  was  dug  the 

parts  to  be  analyzed 
were  ground  in  a  meat 
chopper  and  the  juice 
was  expressed,  when 
necessary,  by  means  of 
a  screw  press.2  Usually 
the  tough  fibers  of  the 
plant  clogged  the  meat 
chopper  and  produced 
a  combined  grinding 
and  pressing  effect. 
The  resulting  pulp  was 
very  dry  and  the  ex- 
pressed sap  could  be 
drawn  off  at  the  oppo_ 
site  end  of  the  grinder 
thus  omitting  the  use 
of  the  press.  Twenty- 
five  cubic  centimeters 
of  the  sap  was  immedi- 
ately pipetted  out  for 
determination  of  reduc- 
ing and  nonreducing 
sugars.  Clarification 
of  the  sap  by  means  of 
neutral  lead  acetate  so- 
lution was  not  always 
successf  ul .  Certain 
plant  substances,  prob- 
ably some  of  the  gums, 
which  failed  to  be  pre- 
cipitated by  the  lead 
acetate  solution,  were 
subsequently  thrown 
down  by  the  Fehlingso- 

ution,  during  the  determination  of  reducing  sugars  as  a  flocculent 

precipitate. 

To  eliminate  this  difficulty  the  following  procedure  was  followed: 

Fifty  cubic  centimeters  of  95  per  cent  ethyl  alcohol  was  poured  into 

25  cubic  centimeters  of  the  freshly  expressed  sap  stirred  continuously. 

This  produced  a  flocculent  precipitate  which  was  easily  filtered  out. 

Fifty  cubic  centimeters  of  the  filtrate  was  pipetted  3  into  a  beaker 

'  This  method  is  subject  to  criticism  when  the  leaves  are  used  because  they  contain  invertase  which 
may  cause  rapid  inversion  of  the  sucrose.  This  trouble  is  reduced  to  a  minimum,  however,  when  only 
stems  and  roots  are  used  because  of  their  very  low  invertase  content.  Evidently  very  little  inversion 
took  place  since  the  hexose  content  in  all  the  leaf  samples  was  very  low.     (See  Table  6.) 

Shrinkage  of  volume,  of  course,  occurs  upon  the  addition  oe  alcohol  to  sap,  which  fact  is  taken  into 
account  when  the  percentage  of  sugars  is  computed. 


Fig.  5. — Four  generations  of  rootstocks.  Note  the  progressive 
change  in  shape  and  tendency  of  the  rootstocks  to  grow  out  of 
the  ground.  Secondary  growth  is  appearing  on  the  first-genera- 
tion rootstock 


CARBOHYDRATE   METABOLISM  AND  GROWTH  IX   EDIBLE  CANNA  7 

and  evaporated  over  a  steam  bath  to  about  15  cubic  centimeters. 
Water  was  then  added  and  the  solution  transferred  to  a  flask  graduated 
to  100  cubic  centimeters  and  clarified  with  neutral  lead-acetate  solution. 
After  this,  the  regular  method  was  adhered  to,  the  reducing  sugars 
being  determined  by  the  method  of  Munson  and  Walker  (1,  p.  78). 4 
Inversion  was  effected  by  allowing  the  solution  to  stand  with  hydro- 
chloric acid  for  12  hours  at  room  temperature.  In  all  cases  the 
hexoses  were  calculated  as  invert  sugar. 

PRESERVATION*    OF    SAP    SAMPLES    FOR    ANALYSIS 

Obviously,  it  was  necessary  to  prevent  changes  in  the  sugars  of 
sap  samples  collected  in  the  field.  In  the  first  trial  25  cubic  centi- 
meters each  of  sap  from  rootstock  and  stem  was  treated  with  formalin 
(40  per  cent  formaldehyde),  stored  for  three  days,  and  analyzed. 
Table  1  shows  the  changes  taking  place  in  the  sugars  of  the  sap  on 
standing  with  formalin  as  a  preservative. 

Table  1. — Effect  of  formalin  (40  per  cent  formaldehyde)  on  the  sugars  of  samples  of 

sap  from  the  canna  plant 


Test 

No. 


Sucrose 


Hexoses 


Source  of  sap  and  treatment  with 
formalin 


Fresh 
sample 


Stored  3       Fresh 
days        sample 


.  /Rootstock  (4  drops) 0.95 

1  \Rootstock  (12  drops) .95  ' 

2  Do 1.01  I 

,  /Stem  (4  drops) .42 

"*  (Stem  (12  drops) j  .42 

4  Do '. .27 


0.86 
.83 
.93 
.13 
.19 
.08 


0.09 
.09 
.15 
.39 
.39 

1.26 


Stored 
days 


Per  cent     Per  cent     Per  cent     Per  cent 


0.21 
.37 
.37 

.72 

.75 
1.56 


Total  sugars 


Fresh       Stored  3 
sample        days 


Per  cent 
1.04 
1.04 
1.16 
.81  i 
.81  J 
1.53 


Per  cent 
1.07 
1.20 
1.30 
.85 
.94 
1.64 


Formalin  did  not  prevent  inversion  of  sucrose,  although  there  was 
no  loss  in  total  sugars  when  it  was  used;  in  fact,  the  total  sugars 
slightly  increased  in  the  juices  treated  with  formalin,  the  percentage 
of  sugars  increasing  with  the  increased  quantities  of  formalin  used. 

Ethyl  alcohol  was  next  tried  as  a  preservative,  25  cubic  centimeters 
of  sap  being  pipetted  into  50  cubic  centimeters  of  95  per  cent  alcohol 
that  had  been  freshly  prepared  by  distillation  with  sodium  hydroxide. 
Two  procedures  were  followed.  In  one  the  samples  were  filtered  at 
once,  and  the  clear  alcoholic  filtrate  stored;  in  the  other  the  unfil- 
tered  samples  were  stored.     Table  2  gives  the  results  of  the  tests. 

Table  2. — Effect  of  ethyl  alcohol  on  the  sugars  of  samples  of  sap  from  the  canna 

plant 


Sam- 
ple 
No. 


Source  of  sap  and  treatment 


1  Stem,  fresh- 

2  Stem,  not  treated,  stored  3  days 

3  Stem,  stored  in  alcohol  3  days,  then  filtered 

4  Stem,  alcoholic  filtrate  stored  3  days 

1  Rootstock,  fresh - 

2  Rootstock,  not  treated,  stored  3  days 

3  Rootstock,  stored  in  alcohol  3  days,  then  filtered. 

4  Rootstock,  alcoholic  filtrate  stored  3  days 


Sucrose 


Per  cent 

0.34 

.02 

.28 

.30 

me 


1. 1.-. 

1.14 


Hexoses 


Per  cent 
1.45 

.71 
1.46 
1.  4.", 
.23 
.07 
.25 
.25 


4  Reference  is  made  by  number  in  italics  to  Literature  cited,  p.  :i4. 


Total 
sugars 


Per  cent 
1.79 

.73 
1.74 
1.75 
1.39 

.07 
1.40 


8 


BULLETIN    56,   HAWAII   EXPERIMENT   STATION 


Ethyl  alcohol,  used  in  the  proportion  of  2  parts  to  1  of  sap,  pre- 
vented changes  in  the  sugars.  The  sugars  largely  disappeared  in  the 
untreated  sap.  Since,  as  the  results  show,  it  is  not  necessary  to  filter 
off  the  alcohol  precipitate  before  storage,  50  cubic  centimeters  of 
alcohol  was  pipetted  into  4-ounce  glass-stoppered  bottles  in  the  lab- 
oratory for  use  in  the  field.  Samples  of  the  canna  plant  were  col- 
lected and  25  cubic  centimeters  of  the  sap  was,  in  each  instance, 

expressed  and  pipetted 
into  the  containers  in 
the  field. 

DETERMINATION    OF    STARCH 

Starch  was  deter- 
mined in  the  dry  samples 
by  the  diastase  method 
recommended  by  the 
Association  of  Official 
Agricultural  Chemists 
(1,  p.  95),  the  resultant 
sugars  being  determined 
by  the  method  of  Mun- 
son  and  Walker  (1,  p. 
78). 

The  specific  gravity 
of  therootstockswas  de- 
termined by  the  West- 
phal  balance,  kerosene 
being  used  as  the  immer- 
sion medium.  The  use 
of  water  was  not  feasi- 
ble because  4;he  differ- 
ence in  its  density  and 
that  of  the  canna  root- 
stock  is  too  small.  The 
latter  sometimes  has  a 
specific  gravity  less  than 
water.  Kerosene,  with 
a  density  of  0.815  at 
room  temperature,  gives 
a  convenient  difference 
in  density,  and  has  the 
additional  advantage 
that  it  causes  portions 
of  the  sap  exuding  from 
the  cut  surfaces  of  the 
rootstock  to  precipitate  undissolved  to  the  bottom  of  the  container. 
The  rootstock  was  suspended  by  means  of  a  fine  wire  connected  with 
a  small  screw  driven  into  the  rootstock.  All  roots,  dead  scales,  and 
adhering  soil,  as  well  as  the  stem,  were  carefully  removed  from  the 
rootstock  before  determination  was  made.  The  removal  of  the  stem 
at  the  exact  apex  of  the  rootstock  is  important  since  the  specific  grav- 
ities of  the  stem  and  the  apical  and  basal  parts  of  the  rootstock  are 


Fig.  6. — Two  generations  of  "spike"  rootstocks  produced  from  a 
single  stem.  A,  the  second  generation,  is  developing  its  stem. 
The  meristem  of  B,  the  first  generation,  was  killed.  The  upper 
part  of  the  parent  stem  was  removed 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN   EDIBLE   CANNA 


9 


very  different.  The  inclusion  of  a  part  of  the  stem  or  the  removal 
of  the  apical  part  of  the  rootstoek  would  thus  introduce  serious 
error  into  the  determination  of  the  specific  gravity  of  the  rootstoek 
as  a  whole. 


SPECIFIC     GRAVITY    AND    ITS    RELATION    TO    STARCH     CONTEXT    OF    ROOTSTOCK     OF 

DIFFERENT    AGES 

The  method  used  to  determine  specific  gravity  has  been  described. 
Table  3  shows  the  variations  in  specific  gravity  of  canna  rootstocks 
grouped  according  to  stage  of  maturity,  generation,  and  age  of  hill. 

Table  3. — Specific  gravity  of  canna  rootstocks  of  different  ages 


=, 

3  months  old 

5  months  old       1    7lA  months  old 

9  months  old 

22  months  old 

0 

o 

Genera- 
tion 

Specific 
gravity 

•  Genera- 
tion 

Specific     Genera- 
gravity         tion 

Specific 
gravity 

Genera- 
tion 

Specific 
gravity 

Genera- 
tion' 

Specific 
gravity 

1 

/First 

\Second  .. 

Third  ... 

1.030    . 
1.088 
1.102    . 



1.080 

First. 

Secon'i  ... 

1.034 
1.000 

First 

Second  ... 

1.065     First 

1.032     Second  .. 
Third... 

1.  073 
1.104 
1.039 
1.054 

2 

1.104 

Third 

.977 

Third 

1.030     Fourth  .. 

Fourth  .. 

Fifth  .... 

Sixth 

Seventh  . 

1.093 
1.073    . 
1.086 
1.061    . 

1.07C 

3a 

3b 

Fourth  . 

.971     Fourth 

.990     Fifth.... 

1.032 

JXot  genealogized.    When  the  hill  reaches  this  staga  it  is  practically  impossible  to  separate  according  to 
generations  because  of  its  size. 

A  number  of  variations  are  evident  in  Table  3.  Each  hill,  consid- 
ered as  a  whole,  showed  a  gradual  rise  in  specific  gravity  with  advanc- 
ing age.  Starting  with  the  3-months-old  hill  having  an  average 
specific  gravity  of  less  than  ] ,  the  specific  gravity  continued  to  rise  to 
the  ninth  month;  thence  to  the  twenty-second  it  varied  slightly.  In 
the  early  growth  of  the  hill  the  first  generation  had  the  highest  specific 
gravity,  each  succeeding  generation  showing  a  decreasing  value.  From 
seven  and  one-half  months  the  second  or  third  generation  had  the 
highest  value;  thence  the  value  continued  to  decrease.  The  specific 
gravity  of  Group  2  was  highest  throughout;  that  of  Groups  3a  and  3b 
decreased,  whereas  that  of  Group  1  was  variable,  but  always  less  than 
in  Group  2.  The  average  specific  gravity  of  the  canna  rootstoek  is 
below  that  of  the  potato  (16),  and  the  range  of  variation  is  much 
greater,  owing  largely  to  the  fact  that  young  and  immature  rootstocks 
as  well  as  mature  ones  are  found  in  every  hill  of  canna,  regardless  of 
its  age. 

To  ascertain  the  relationship  between  the  specific  gravity,  deter- 
mined by  the  method  outlined  by  Wiley  (16,  pp.  369-371),  and  the 
other  constituents  of  the  canna  rootstoek,  a  series  of  analyses  was 
made  of  hills  of  different  ages  and  from  different  localities.  Table  4 
shows  the  relationship  of  the  specific  gravity  to  the  starch,  dry  mat- 
ter, and  solids  other  than  starch  in  the  canna  rootstoek. 

35973—27 2 


10 


BULLETIN   56,   HAWAII  EXPERIMENT   STATION 


Table  4. — Relation   of   the   specific   gravity  of  rootstocks,  as  shown   by  stage  of 
maturity,  to  their  starch  content  and  other  constituents 

HILL  A  (12  MONTHS  OLD),  STATION  FIELD  26A 


6 

Genera- 
tion 

Stage  of  maturity 

Moisture 

Dry  mat- 
ter 

Starch  in 

Solids 
other 
than 

starch . 

Specific 
gravity 

E 

eS 

Green 
weight 

Dry 
weight 

1 

Group  1... 

Per  cent 
55.30 
70.72 
73.91 
82.70 
84.58 

Per  cent 
44.70 
29.28 
26.09 
17.30 
15.42 

Per  cent 
21.30 
22.53 

Per  cent 
70.03 
76.  93 

Per  cent 
13.40 
6.75 
6.17 
6.18 
6.46 

1.056 

? 

Old  Group  2 

1. 106 

3 

Old  Group  3a 

19.92  1        76.36 

11.  12           64. 30 

8.96           58.11 

1.094 

4 

Young  Group  3a 

1.033 

5 

Group  3b  (spike) 

1.012 

HILL  B  (7lA  MONTHS  OLD),  STATION  FIELD  26B 


10 


First... 
Second 
Third- 
Fourth 
Fifth  .. 


Old  Group  2 . 

Medium  Group  2 .. 
Young  Group  3a.. 
Medium  Group  3a . 
Young  Group  3a... 


70.15 

29.85 

17.49 

58.58 

12.36 

63.90 

36.10 

28.81 

79.81 

7.29 

68.22 

31.78 

22.83 

71.83 

8.95 

79.46 

20.54 

15.18 

73.89 

5.36 

86.40 

13.60 

9.47 

69.64 

4.13 

1.073 
1.104 
1.089 
1.054 
1.032 


HILL  C  (3M  MONTHS  OLD),  STATION  FIELD  32C 


11 

First.... 
Second  . 
Third  .. 
Fourth  . 
...do.... 

Medium  Group  2 

80.52 
85.52 
87.42 
90.42 
91.92 

19.48 
14.48 
12.58 
9.58 
8.08 

11.51 
7.75 
7.20 
4.59 
2.58 

59.08 
53.54 
57.20 
47.91 
31.87 

7.97 
6.73 
5.58 
4.99 
5.50 

1.034 

n 

Young  Group  2 

1.000 

13 
14 

Medium  Group  3a 

Young  Group  3a 

.977 
.974 

15 

Group  3b  (spike) 

.971 

HILL  S  (11  MONTHS  OLD),  WAIMEA  FIELD  S 


16 

First 

17 

Second  . 

18 

Third... 

19 

Fourth  . 

20 

...do.... 

21 

...do.... 

22 

Fifth  ...! 

?3 

?4 

1 

Group  1 

Old  Group  2 

Medium  Group  2 

Young  Group  3a  (old)  .. 

....do . 

....do 

Spike,  dead 

Young  Group  3a  (fresh) 
do 


65.23 

34.77 

27.42 

78.85 

7.35 

65.25 

34.75 

27.92 

80.35 

6.83 

70.47 

29.53 

24.41 

82.65 

5.12 

85.71 

14.29 

9.42 

65.94 

4.87 

85.86 

14.14 

9.83 

69.52 

^.31 

80.17 

19.83 

13.60 

68.58 

6.23 

75.20 

24.80 

18.59 

74.96 

6.21 

90.68 

9.32 

4.51 

48.37 

4.81 

92.79 

7.21 

2.08 

28.85 

5.13 

1.097 
1.115 
1.104 
1.021 
1.027 
1.051 
1.076 
.972 


A  distinct  correlation  between  specific  gravity  and  starch  and  other 
constituents  is  apparent.  Certain  discrepancies  exist,  particularly 
with  respect  to  the  first  generation  rootstocks,  which  were  characterized 
by  unusually  high  solids  other  than  starch.  In  the  older  hills  the  specific 
gravities  of  such  rootstocks  were  less  than  of  second  generation  root- 
stocks,  and  bore  slight  relation  to  the  percentages  of  starch.  As  pre- 
viously stated  (p.  2),  this  kind  of  rootstock  is  materially  different  in 
manner  of  growth  from  the  other  rootstocks  in  the  hill,  and  since 
only  one  or  two  grow  in  each  hill,  they  may  be  disregraded  in  con- 
sidering the  hill  as  a  whole.  Although  the  solids  other  than  starch 
did  not  vary  widely,  they  showed  a  distinct  tendency  to  follow  the 
specific  gravity  curve.  The  relationship  between  these  several  con- 
stituents is  evident,  particularly  in  case  of  hill  S  (fig.  13),5  in  which 
the  percentages  dropped  suddenly  in  the  fourth  generation,  increased 
in  the  fifth,  and  dropped  again  in  the  sixth  generation. 


5  The  first  generation  of  each  hill  is  omitted  from  figs.  13  and  14. 


CARBOHYDRATE  METABOLISM    AND   GROWTH  IN   EDIBLE  CANNA        H 

If  the  specific  gravity  and  starch  content  of  the  several  hills  are 
plotted  as  separate  curves  (fig.  14),  each  hill  would  seem  to  have 
what  might  be  termed  a  characteristic  "growth  curve,"  the  location 
and  nature  of  which  depends  upon  a  number  of  factors,  including  age, 
rainfall,  and  rapidity  of  growth. 

The  curve  of  hill  S,  from  Waimea  rootstocks,  covering  a  wide  range 
of  percentages  and  lying  about  midway  of  the  curves  of  hills  A  and  B, 
was  adopted  for  field  studies  and  mill  control.  Table  5,  taken  from 
the  curve  of  hill  S,  shows  the  approximate  starch  content  of  root- 
stocks  as  ascertained  by  the  specific  gravity. 

Table  5. — The  starch  content  of  rootstocks  as  determined  by  specific  gravity 


Specific 

Starch  in 

Specific 

Starch  in 

Specific 

Starch  in 

gravity 

rootstock 

gravity 

rootstock 

gravity 

rootstock 

Per  cent 

Per  cent 

Per  cent 

0.98 

3.5 

1.03 

10.2 

1.08 

18.7 

.99 

4.7 

1.04 

11.7 

1.09 

20.9 

1.00 

6.0 

1.05 

13.3 

1.10 

23.3 

1.01 

7.4 

1.06 

15.0 

1.11 

26.1 

1.02 

8.8 

1.07 

16.8 

1.12 

30.3 

Determination  of  the  starch  content  of  a  rootstock  by  its  specific 
gravity  is  admittedly  only  approximate.  The  only  varying  factors 
considered  are  starch  and  water;  differences  in  structure  or  of  air 
spaces  within  the  rootstock  are  not  taken  into  account.  The  latter, 
particularly,  introduces  appreciable  error  in  the  determination.  The 
specific  gravity  of  a  canna  rootstock  may  be  increased  from  1.07  to 
1.12  and  higher  by  placing  the  rootstock  in  water  and  evacuating. 
Notwithstanding  these  imperfections  the  method  has  much  practical 
value  in  both  field  and  factory.  Obviously,  its  accuracy  depends 
upon  the  number  of  analyses  from  which  the  table  is  constructed, 
and  many  additional  analyses  will  have  to  be  made  before  a  thor- 
oughly reliable  table  can  be  made. 


CARBOHYDRATE  METABOLISM 

Variations  in  the  sugars  of  the  sap  of  the  canna  plant  offer  special 
advantages  to  the  chemist  in  studying  its  methods  of  growth  as  a 
starch  crop.  The  relationship  between  the  sugars  and  the  growth  of 
the  plant  can  be  learned,  as  well  as  the  various  changes  taking  place 
in  form  and  concentration  of  the  sugars  during  translocation  and  ulti- 
mate storage  as  starch. 

Study  of  the  occurrence  of  sugars  in  the  metabolism  of  the  plant 
and  their  significance  began  with  the  discovery  by  Sachs  (12)  in  1862 
of  starch  in  the  chlorophyll-granule  and  his  conclusion  that  starch 
disappears  from  the  leaf  by  conversion  into  sugar.  Schimper  (13) 
modified  Sach's  hypotheses  by  stating  that  glucose  formation  precedes 
starch  formation  in  the  leaf,  and  that  starch  is  formed  from  glucose 
when  its  concentration  exceeds  a  certain  maximum,  which  varies  in 
different  plants. 

Meyer  (10)  observed  that  the  leaves  of  many  plants  contain  no 
starch,  and  that  such  leaves  usually  have  a  high  sugar  concentration 
compared  with  those  containing  starch.  Later,  Brown  and  Morris 
(2),  using  more  exact  chemical  methods,  studied  the  nature  of  the 


12 


BULLETIN    56,    HAWAII   EXPERIMENT    STATION 


sugars  and  found  that  the  reducing  sugars,  which  up  to  that  time 
had  been  considered  as  glucose,  consist  of  both  levulose  and  dextrose. 
The  presence  in  the  leaf  of  large  quantities  of  sucrose  and  the  nature 
of  its  fluctuations  led  to  the  conclusion  that  sucrose  is  the  first  sugar 
produced  by  photosynthesis,  and  that  levulose  and  dextrose  are  the 

products  of  hydrolysis 
of  the  sucrose. 

Davis,  Daish,  and 
Sawyer  (6) ,  in  studying 
the  carbohydrates  of  the 
mangel  leaf,  and  Davis 
and  Sawyer  (5),  in 
studying  the  potato 
plant,  found  that, 
whereas  in  the  leaf 
sucrose  predominates, 
the  hexoses  are  in  excess 
of  the  sucrose  in  the 
midribs  and  stems. 
From  this  they  con- 
cluded that  sucrose  is 
the  "  primary  sugar 
formed  in  themesophyll 
of  the  leaf  under  the 
influence  of  the  chloro- 
phyll," and  that  "it  is 
transformed  into  hex- 
oses for  the  purpose  of 
translocation"  (6,  p. 
314).  Strakosch  (14) 
took  the  opposite  view. 
Using  mic'rochemical 
methods,  he  concluded 
that  dextrose  is  the  first 
apparent  sugar  to 
appear.  The  appear- 
ance of  levulose,  and 
later  of  sucrose  in  the 
leaf  veins,  led  him  to 
believe  that  sucrose  is 
the  final  sugar  and  is 
transported  as  such 
through  the  stem. 
Pellet,  in  a  discussion 
with  Vivien  (15,  p.  173),  concludes  that  sucrose,  dextrose,  and 
levulose  are  formed  simultaneously  in  the  leaf  and  descend  to  the  root 
as  such. 

The  variations  of  sugars  at  different  stages  of  maturity  of  the 
plant  have  been  studied  by  different  investigators.  Colin  (4)  found 
that,  in  the  early  stages  of  growth  of  the  sugar  beet  root,  the  reducing 
sugars  may  form  as  much  as  20  per  cent  of  the  total  sugars.  As  the 
root  matures  the  proportion  of  reducing  sugars  to  sucrose  decreases, 
but  the  former  are  never  entirely  absent  and  are  always  most 
abundant  at  the  growing  tip.     Davis  (6)  and  his  associates,  work- 


Fig.  7.— Different  stages  in  the  development  of  the  bud.  The 
stem  of  the  large  offspring  is  developing,  resulting  in  a  sharp 
decrease  in  cell  growth  at  the  apex  of  the  rootstock.  This  has  led 
to  vigorous  development  of  its  bud.  The  bud  on  the  parent 
rootstock  has  failed  to  develop,  and  probably  would  eventually 
result  in  a  small  secondary  rootstock 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA        13 

ing  with  the  mangel,  found  that  during  the  early  stages  of  growth, 
when  leaf  formation  is  the  main  function,  sucrose  exceeds  the  hex- 
oses  in  the  leaves,  but  that  later  in  the  season,  when  sugar  is  being 
stored  in  the  root,  the  hexoses  predominate.     They  further  noted 


Fig.  8— Effect  of  parent  stem  on  offspring.  Left,  stunted  secondary  growth  with  parent  stem  dead; 
center,  upper,  first  generation  roctstcck  attached  to  seed.  This  small,  cylindrical  type  has  only  the 
seed  to  support  its  growth.  Center,  lower,  two  stunted  offspring  with  no  parent  stem,  it  having 
been  removed  several  months  previous:  and  right,  two  vigorous  offspring  with  good  parent  stem 


Fig.  9.— The  progressive  changes  in  shape  of  rootstocks  in  the  hill.  A,  original  seed  with  first  gener- 
ation cylindrical  rootstock  attached;  B,  second  generation,  small,  intermediate  type;  C,  third  gen- 
eration, large,  intermediate  type;  D,  fourth  generation,  surface  type;  E,  fifth  generation,  surface 
type;  spike  rootstock,  partly  developed 

that  the  hexoses  always  are  in  excess  of  sucrose  in  the  midribs  and 
stems,  and  that  the  ratio  of  hexoses  to  sucrose  increases  rapidly  in 
passing  down  the  stem  to  the  root.  The  hexoses  vary  greatly  dur- 
ing the  day  and  night  and  throughout  the  season,  whereas  the  sucrose 


14 


BULLETIN    56,   HAWAII   EXPERIMENT    STATION 


remains  practically  constant.  Although  the  mangel  is  not  a  starch- 
storing  crop,  starch  is  found  in  its  leaves  in  the  early  stages  of 
growth,  and  disappears  permanently  as  soon  as  the  root  begins  to 
develop. 

In  studying  the  variations  in  the  carbohydrates  of  the  leaves  of  the 
potato  plant  during  a  24-hour  period,  Davis  and  Sawyer  (5)  observed 
that  the  sucrose  in  the  leaves  reaches  its  maximum  at  2  p.  m. 
Subsequent  decrease  is  accompanied  by  an  increase  in  the  hexoses 
and  the  appearance  of  soluble  starch  in  the  leaves,  indicating  a 
change  of  sucrose  into  invert  sugar  and  subsequent  condensation  into 
starch.     The  starch  decreases  during  the  afternoon  and  early  part  of 

the  night,  reaching  a 
very  low  value  between 
midnight  and  2  a.  m., 
apparently  being  con- 
verted into  hexoses. 

Miller  (11),  working 
with  the  leaves  of  corn 
and  sorghum,  noted  that 
the  nonreducing  sugars 
increase  during  the  day 
and  decrease  during  the 
night;  whereas,  the  vari- 
ations in  the  reducing 
sugars  are  comparatively 
small  and  very  irregular. 
The  insoluble  carbohy- 
drates, reaching  a  maxi- 
mum later  in  the  day 
than  the  sugars,  decrease 
rapidly  after  midnight. 

VARIATIONS  IN  DIFFERENT 
PARTS  OF  THE  PLANT 

Analyses  were  made 
to  determine  the  nature 
of  the  carbohydrates 
formed  by  photosyn- 
thesis in  the  leaf  of  the 
canna  plant,  and  any 
change  taking  place  during  transposition  through  the  stem  to  their 
final  deposition  as  starch  in  the  rootstock.  The  sap  was  extracted 
from  a  fresh  part  of  each  sample6  and  the  sugars  were  determined  as 
outlined  under  "  Laboratory  Methods,"  p.  6.  The  remainder  of  some 
of  the  samples  was  dried  and  ground,  and  the  percentage  of  moisture 
and  starch  was  determined.     Table  6  gives  the  results  of  the  analyses. 


Fig.  10.— Method  of  development  of  buds.  Longitudinal  section 
of  a  portion  of  a  young  surface  rootstock.  The  bud  develops 
at  the  base  of  the  scale.  The  vascular  bundles  supporting  its 
growth  are  to  be  seen  extending  far  into  the  iuterior.  Under 
normal  conditions,  B  and  C  develop  as  vigorous  primary  growth, 
whereas  A  either  fails  to  develop  or  appears  as  secondary  growth 
at  a  later  period,  when  it  is  known  as  a  "top  bud" 


6 These  and  subsequent  samples  for  sugar  determination  were  dug  between  9  and  12  a.  m.  While  the 
time  of  sampling  has  a  decided  effect  on  the  sugar  content  of  the  leaves  of  a  plant,  the  stems  and  roots  are 
much  less  subject  to  daily  variation.  The  results  obtained  would  hardly  be  materially  affected  by  the 
time  of  taking  the  sample  in  the  case  of  the  stem  and  rootstock. 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA        15 

Table  6. — Composition  of  different  parts  of  the  carina  plant 
HILL  NO.  1  (11  MONTHS  OLD),  STATION  FIELD  26C 


6 

05 

= 
03 
CO 

Source  and  parts  of  the  individual 
plant 

Mois- 
ture 

Dry 

matter 

Starch 

Green       Dry 
weight    weight 

Solids 
other 
than 
starch 

Sucrose 
in  sap 

Hexoses 
in  sap 

Total 
sugars 
in  sap 

1 

Group  1: 

Btem 

Per  cent 
91.96 
68.25 
66.67 

77.20 
89.20 
90.46 
72.62 
66.91 

92.91 
84.88 
78.75 

Per  cent 

8.04 

31.75 

33.33 

22.80 
10.80 

Per  cent 

Percent 

Per  cent 

Per  cent 
0.45 

1.57 

1.47 

1.54 
.94 
1.18 
2.53 
1.87 

.32 
1.09 
1.15 

Per  cent 
0.82 
.25 
.03 

.11 
1.50 
2.55 
.77 
.09 

.29 
.43 
.29 

Per  cent 
1.27 

■) 

Rootstock  (apex) l 

23.11 
26.18 

72.78 
78.54 

8.64 
7.15 

1  82 

3 

Rootstock  (base) ' 

1.  50 

4 

Group  2: 

Leaves 

1.65 

Midribs  and  sheaths 

2.44 

6 

Stem 

9.54 

3.73 

7 

Rootstock  (apex) 

27.38 
33.09 

7.09 
15.12 
21.25 

20.29       74.09 
26.  53       80.  19 

iSS 

3.30 

8 

q 

Rootstock  (base) 

Young  Group  3a: 

1.96 
.61 

10 

Rootstock  (apex) 

9.  90       65.  45 

5.22 
7.32 

1.52 

n 

Rootstock  (base) 

13.93 

65.54 

1.44 

HILL  NO.  2  (7  MONTHS  OLD),  STATION  FIELD  26B 


1? 

Group  2: 

Leaves 

1.30 
.87 
1.68 

1.49 
.63 

1.00 

.75 

0.25 
1.18 
2.48 

.18 
1.33 

.04 
.39 

1.55 

13 

Midribs  and  sheaths  

2.05 

14 

Stem 

4.  16 

15 

Group  3a: 

Leaves 

1.67 

16 

Midribs  and  sheaths ... 

1.96 

17 

Young  Group  3a- 

1.04 

IS 

Midribs  and  sheaths -. 

1. 14 

HILL  NO.  3  (3  MONTHS  OLD),  STATION  FIELD  32C 


Old  Group  3: 

Leaves 

Midribs  and  sheaths 92.00 

Stem 94.72 

Rootstock 


82.29 

17.71 

0.248 

1.40 

17.46 

2.61 

0.04 

92.00 

8.00 

.035 

.44 

7.96 

.78 

.59  ' 

94.72 

5.28 

.030 

.56 

5.  25 

.25 

.82 

89.27 

10.73 

4.900 

45.70 

5.83 

2.13 

.57 

2.65 
1.37 
1.07 
2.70 


HILL  NO.  4  (12  MONTHS  OLD),  WAIMEA  FIELD  W-S 


Old  Group  2: 

Rootstock  (apex). 

Rootstock  (base)  . 
Group  3a: 2 

Rootstock  (apex) . 

Rootstock  (base)  . 
Group  3b:  * 

Rootstock  (apex) . 

Rootstock  (base) 


0.70 
.60 


1.20 
1.30 


1.20 


0.21 
.04 


1.02 
.76 


1.  55 
1.22 


0.91 
.64 


2.22 
2.06 


2.30 
2.42 


1 "  Apex  "  denotes  the  apical  and  "  base  "  the  basal  half  of  the  rootstock. 

1  Groups  3a  and  3b  samples  of  hill  No.  4  were  exceptionally  vigorous  and  large. 

Samples  Nos.  4  to  8,  inclusive,  Group  2,  hill  1,  showed  the  com- 
plete series  of  changes  taking  place  in  a  mature  plant  from  the  for- 
mation of  sugars  in  the  leaves  by  photosynthesis  to  the  storage  of 
sugars  as  starch  in  the  basal  part  of  the  rootstock.  Starting  with 
the  leaves  (fig.  15),  the  hexoses  increased  rapidly  in  progressing  down 
the  sheaths,  midribs,  and  through  the  stem  proper,  then  decreased 
in  the  apical  part  of  the  rootstock,  finally  falling  practically  to  the 
same  level  in  the  basal  part  as  in  the  leaves.     The  sucrose  started 


16 


BULLETIN   56,   HAWAII   EXPERIMENT   STATION 


with  a  relatively  high  percentage  in  the  leaves,  dropped  in  the  mid- 
ribs and  sheaths,  rose  in  the  apical  part  of  the  rootstock,  and  dropped 
again  in  the  basal  part.  The  total  sugars  had  the  same  curve  as  the 
hexoses,  although  the  variation  was  relatively  small. 

The  leaves  and  sheaths  of  Group  1,  hill  1,  samples  Nos.  1,  2,  and  3, 
were  dead  and  the  stem  was  shrivelling  at  the  apex.  The  sugars  in 
the  remaining  part  of  the  stem  showed  a  ratio  similar  to  that  of  the 
sugars  of  the  stem  of  Group  2,  although  the  quantity  of  each  was 
considerably  less.  The  total  sugars  within  the  rootstock  were  dis- 
tinctly less  than  in  Group  2,  particularly  in  the  apical  part. 

The  stems  of  young  Group  3a,  hill  1  (samples  Nos.  9,  10,  and  11) 
had  not  developed*  to  any  appreciable  extent  and  were  immature, 
and  the  leaves  were  appearing  at  the  top.  The  midribs  and  sheaths 
showed  a  very  striking  decrease  in  sugars  as  compared  with  Group  2, 


Fig.  11.— Secondary  growth  in  a  field  of  stunted  plants  12  months  old.  Severe  drought  practically 
destroyed  stem  growth.  The  developing  secondary  growth  is  very  stunted  with  small  undersized 
rootstocks 

particularly  in  the  hexoses,  which  fell  below  the  sucrose;  and  the 
relationship  between  the  apical  and  basal  parts  of  the  rootstock  was 
different  from  that  of  the  preceding  groups.  Sucrose  increased  from 
apex  to  base,  whereas  in  Groups  1  and  2  it  decreased.  In  the  basal 
portions  of  these  latter  groups  the  hexoses  were  extremely  low,  but 
in  Group  3a  they  were  present  in  appreciable  and  only  slightly  less 
quantities  than  in  the  apical  part. 

In  hill  2  (samples  Nos.  12  to  18,  inclusive)  the  stems  showed  a 
striking  similarity  to  those  of  hill  1.  Sample  No.  14,  a  Group  2  stem, 
showed  the  same  increase  in  sucrose  over  midribs  and  sheaths  as  was 
noted  in  sample  No.  6,  hill  1.  Likewise,  the  midribs  and  sheaths  of 
young  Group  3a  showed  a  low  concentration  of  hexoses  similar  to 
that  of  sample  No.  9,  hill  1.  The  proportions  of  sugars  of  the  leaves 
of  Group  2,  hill  2,  old  Group  3a,  hill  3,  and  Group  2,  hill  1,  were  very 


CARBOHYDRATE   METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA       17 


similar.  Notwithstanding  a  distinct  falling  off  in  the  quantity  of 
both  sugars  in  the  loaves  of  young  Group  3a,  hill  2,  the  ratio  was 
practically  the  same. 

Samples  Xos.  19  to  22,  inclusive,  old  Group  3a,  hill  3,  showed  the 
same  general  composition  and  changes  of  sugars  in  transposition 
noted  in  hills  1  and  2.  A  number  of  significant  differences  occurred, 
however.  The  leaves  were  distinctly  higher  in  sucrose  but  very  low 
in  hexose  content.  Sucrose  continued  to  decrease  in  passing  from 
midribs  and  sheaths  into  stem  whereas  in  the  mature  plants  of  hills 
1  and  2  it  always  increased.  The  total  sugars  decreased  sharply 
in  passing  from  the  leaves  downward  into  the  stem,  whereas  in  hills 
1  and  2  the  reverse  was  true.  The  rootstock  was  outstandingly 
higher  in  sucrose  as  compared  with  Group  3a,  hill  1.     The  stem  of 


Fig.  12.— The  result  of  stunting.  A,  B,  C,  and  D  represent  the  first,  second,  third,  and  fourth  genera- 
tions, respectively.  Note  the  profusion  of  small,  stunted  "secondary"  growth  on  all  generations 
except  the  first 

the  plant  contained  starch  in  appreciable  quantities  throughout, 
whereas  the  stems  of  the  other  hills,  even  in  young  Group  3a,  hill  2, 
contained  only  traces  of  starch. 

Samples  Nos.  23  to  28,  inclusive,  hill  4,  from  Waimea,  showed  the 
extreme  variations  occurring  within  a  single  hill.  Samples  Nos.  23 
and  24,  the  apical  and  basal  parts  of  a  rootstock  the  stem  of  which 
was  practically  dead,  were  very  low  in  sucrose  and  hexose  content. 
Both  sugars  increased  greatly,  particularly  the  hexose,  in  samples 
Nos.  25  and  26,  a  vigorous  Group  3a  rootstock.  This  increase  con- 
tinued, the  hexoses  exceeding  the  sucrose,  in  samples  Nos.  27  and  28, 
a  vigorous  Group  3b  rootstock.  In  Groups  2  and  3a,  the  total  sugars 
decreased  in  passing  from  the  apical  to  the  basal  part,  whereas,  in 
Group  3b,  they  slight ly  increased.     The  basal  part  of  the  Group  2 

35973—27 3 


18 


BULLETIN   56,   HAWAII   EXPERIMENT   STATION 


//oo  * 


/OSO 


9SO 


rootstock  was  lower  than  the  apical  part  in  sucrose  content,  whereas 
the  reverse  was  true  in  Groups  3a  and  3b.  The  hexose  content  of  the 
apical  parts  of  all  three  groups  was  higher  than  the  basal.  Although 
the  actual  percentage  of  each  was  radically  different  from  those  of 
the  rootstocks  of  hill  1,  grown  at  the  station,  the  above-mentioned 
relations  held  true  in  the  latter. 

Some  very  distinct  differences  were  apparent  in  the  variations  of 
the  components  other  than  sugars  in  hills  1  and  3.  In  Groups  1  and 
2,  hill  1,  the  average  total  dry  matter  and  starch  content  of  the  root- 
stock  were  practically  the  same,  whereas  in  Group  3a  they  showed  a 
sharp  decrease.     The  percentage  of   starch  in  the  dry  matter  also 

decreased.  In  all  three 
groups  the  basal  part 
of  the  rootstock  con- 
tained the  larger 
quantity  of  starch.  In 
Groups  1  and  2  the  pro- 
portion of  starch  in  the 
total  dry  matter  was 
distinctly  greater  in  the 
basal  part,  whereas  in 
the  Group  3a  rootstock 
the  percentage, 
although  lower  than  in 
the  former  groups,  was 
practically  the  same 
in  both  parts.  Hill  3 
was  noticeably  very 
low  in  average  total 
dry  matter  and  starch 
content  of  both  root- 
stock  and  dry  matter. 
Table  6  presents  some 
very  definite  evidences 
as  to  the  nature  of  the 
sugars  of  the  canna 
plant  and  the  changes 
occurring  in  their  trans- 
location from  the  leaves 
to  the  rootstock.  The 
chief  sugar  of  the  leaves 
is  sucrose  with  a  small 
The  hexose-sucrose  ratio 
age  of  the  hill  and  the 


20 


30 


/O 


S/>1 

-C/F/C 

gz/iw 

TV 

ST/) 

ecH 

> 

o/er  / 

v/irn 

~e 

\ 

\ 

so 

L/DS  OTHE/9 

TH/W 

ST/7£ 

CH 

/a 


/9  20  2/ 

SAMPLE  MUMBEG 


22 


Fig.  13.— Relation  of  specific  gravity  to  starch,  dry  matter,  and 
solids  other  than  starch  in  c^nna  rootstocks 


but  ever  present  quantity  of  the  hexoses. 
remains  consistently  low  regardless  of  the 

stage  of  maturity  of  the  plant.  This  is  notable  in  considering  the 
data  of  Davis  and  Sawyer  (5),  who  found,  in  case  of  the  potato  plant, 
that  although  sucrose  predominates  in  early  growth,  the  hexoses 
exceed  sucrose  in  later  growth  when  translocation  rather  than  growth 
is  the  principal  function  of  the  leaves;  whereas,  the  results  of  Lutman 
(9)  and  Miller  (11)  show  very  little  correlation  between  the  reducing 
and  nonreducing  sugars  of  the  leaves. 


CARBOHYDRATE  METABOLISM  AXD  GROWTH  IN  EDIBLE  CANNA        19 


The  method  of  extracting  sap  by  means  of  a  meat  grinder  and 
screw  press  is  not  well  adapted  to  the  leaves  of  the  canna  plant 
because  the  sap  is  very  viscous.  Moreover,  it  was  necessary  to  use 
all  the  leaves  from  a  single  stem  to  obtain  enough  sap  for  a  deter- 
mination. Possibly  a  more  complete  extraction,  using  greater  pres- 
sure as  is  suggested  by  Knudson  and  Ginsburg  (8),  might  affect  the 
results  somewhat.  The  constancy  of  the  data  would  seem  sufficient 
to  substantiate  the  essential  correctness  of  the  conclusions  drawn, 
however. 

The  very  rapid  rise  of  the  hexoses  and  the  decrease  of  sucrose  in 
the  midribs  and  sheaths  and  the  continuation  of  these  changes  in  the 


/./20 


/2  /5  /8  2/         24 

peg  cs/vr  or  sr^ecn 

Fig.  14.— Relation  of  specific  gravity  to  percentage  of  starch  in  canna  rnot.stocks 

stems  is  strong  evidence  in  favor  of  the  hexoses  as  '  ..■  ugars  con- 
cerned in  translocation.  This  is  in  accord  with  the  finding  *  of  Davis 
and  Sawyer. 

In  the  stems  of  Group  2,  hills  1  and  2,  the  hexoses  still  great  I  v 
exceeded  the  sucrose,  but  the  latter  showed  an  increase  in  concen- 
tration over  that  of  the  sheaths  and  midribs.  This  probably  resulted 
from  the  functioning  of  the  stem  as  a  temporary  storage  organ.  In 
the  stem  of  the  younger  plant,  hill  3,  no  such  phenomenon  occurred, 
the  sucrose  decreasing  to  a  very  low  percentage.  Evidently  no  stor- 
age of  sugars  occurred;  in  fact,  the  total  sugars  very  markedly 
decreased.  In  explanation  it  may  be  said  that  the  stem  was  in  proc- 
ess of  rapid  growth  during  which  food  material  was  not  stored,  but 
rather  diverted  toward  the  apex  of  the  stem. 


20 


BULLETIN    56,   HAWAII   EXPERIMENT   STATION 


In  all  instances  the  sucrose  suddenly  increased  upon  reaching  the 
rootstock  and  the  hexoses  correspondingly  decreased.  This  fact  fur- 
ther confirms  the  conclusion  that  inversion  of  sucrose  to  hexoses  is  pri- 
marily for  the  purpose  of  translocation.  The  hexoses  again  decreased 
rapidly  toward  the  basal  part  of  the  rootstock.  They  were  seldom 
entirely  wanting,  and  were  found  in  smallest  quantity  in  regions  where 
translocation  was  at  a  minimum  and,  likewise,  in  greatest  quantity 
where  it  was  at  a  maximum,  confirming  the  opinion  that  they  prac- 
tically alone  effect  translocation.  In  the  basal  part  of  the  rootstock 
sucrose  decreases,  of  course,  as  the  result  of  its  condensation  into 
starch.  The  occurrence  of  sucrose  in  very  appreciable  quantities  in 
the  rootstock,  regardless  of  age,  suggests  that  it  is  essentially  intra- 
cellular, the  true  intermediate  product  between  the  hexoses  and  starch, 
and  in  some  sort  of  equilibrium  with  the  latter. 

The  hexoses  are  abundantly  present  in  both  young,  and  the  apical 
part  of  old,  rootstocks  as  compared  with  the  basal  part  of  old  root- 
stocks,  a  fact  offering 
further  evidence  that 
reducing  sugars  are  al- 
ways associated  with 
growth .  This  bears  o  ut 
the  observation  of  Colin 
with  the  sugar  beet  (4) 
that  the  hexoses  are 
always  found  at  the 
growing  points. 

The  finding  of  starch 
in  various  parts  of  the 
stems  of  hill  3,  together 
with  a  very  low  per- 
centage of  starch  in  the 
rootstock,  .whereas 
starch  was  found  only 
in  negligible  quantities 
in  the  stem  of  the  older 

Fig.15.— Sugars  in  different  parts  of  the  plant  hills     is    in   aCCOrd   with 

the  observations  of  Davis,  Daish,  and  Sawyer  (6),  who  showed  that 
starch  forms  in  the  leaves  of  the  mangel  plant  only  during  its  very 
early  growth.  In  explanation  of  this  phenomenon  they  advanced 
the  hypothesis  that  starch  was  stored  in  the  leaves  because  the  root 
of  the  mangel  had  not  yet  developed,  but  that  as  soon  as  sugar  began 
to  be  deposited  in  it  the  starch  disappeared  from  the  leaves  and  did 
not  reappear. 

VARIATIONS  IN  THE  SAME  HILL 

A  number  of  hills  of  different  ages  were  classified  and  genealogized 
in  the  usual  manner  to  correlate  the  variations  taking  place  in  the 
composition  of  the  plants  with  the  growth  of  the  hill  in  the  field. 
Representative  plants  from  each  generation  were  selected  for  deter- 
mination of  their  sugars  and  some  other  constituents.  Table  7  gives 
the  results  of  the  analysis  of  the  stem7  and  the  rootstock. 


SHCATHS 


eooTsroc/r  eoorsroc/c 

s4P/Cs4L  Ps4/er  B/IS/IL  P^GT 


7  The  term  "stem"  is  here  used  to  include  the  sheaths  and  the  stem  proper,  the  leaves  and  the  midribs 
being  discarded.  To  obviate  the  possibility  of  includiug  a  part  of  the  stem  with  the  rootstock,  and  vice 
versa,  a  section  of  the  apical  part  of  the  rootstock  and  the  lower  part  of  the  stem,  about  2  inches,  was 
discarded. 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA       21 


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BULLETIN   56,   HAWAII   EXPERIMENT   STATION 


In  hill  1,  11  months  old,  sample  No.  3,  the  rootstock  and  stem  of 
an  old  Group  2  plant,  contained  the  maximum  total  sugar.  (Fig.  16.) 
In  this  stage  all  new  growth  had  ceased  and  the  lower  leaves  of  the 
plant  had  died,  leaving  only  the  apical  leaves  to  function.  Through- 
out subsequent  generations  the  sugars  decreased  rapidly.  In  the  stem 
of  sample  No.  5,  Group  3a,  which  was  still  growing  at  the  top,  both 
sucrose  and  the  hexoses  sharply  decreased.  Sucrose  remained  low 
and  constant  in  the  stem  throughout  Group  2,  whereas  the  hexoses 
were  much  higher.  The  reverse  was  true  of  the  rootstock,  the  hexose 
content  being  very  low  and  constant  throughout  Groups  1  and  2, 
with  the  sucrose  content  much  higher  and  more  variable.  Sucrose 
decreased  in  sample  No.  6,  Group  3b,  whereas  the  hexose  content  was 
double  that  of  sample  No.  5.     A  comparison  of  the  total  sugars  in 

the  rootstock  and  the 
stem  shows  that  in  the 
Group  2  stage  the  stem 
had  a  greater  concentra- 
tion than  the  rootstock, 
whereas  in  Group  3a 
the  reverse  was  true, 
although  in  most  cases 
the  differences  were 
small.  Marked  varia- 
tions also  occurred  in 
the  other  constituents. 
The  rootstock  of  sample 
No.  3  contained  the 
maximum  dry  matter 
and  starch  content,  both 
of  green  and  dry  weight, 
and  also  the  maximum 
sugar  content.  These 
values  were  remarkably 
constant  in  samples 
Nos.  2,  3,  and  4,  Groups 
1  and  2.  Sample  No.  5, 
a  Group  3a  rootstock, 
showed  a  decrease,  and  sample  No.  6,  a  Group  3b  rootstock,  a  very 
sharp  decrease.  The  solids  other  than  starch  showed  a  similar  de- 
crease, except  that  the  maximum  value  was  in  sample  No.  1,  the 
first  generation  rootstock. 

A  consideration  of  hill  2,  7  months  old,  shows  that  it  closely 
resembles  hill  1,  in  an  adjacent  field,  except  that  the  sucrose  of  the 
stems  of  Group  2  was  higher.  The  decrease,  rather  than  increase,  of 
the  hexoses  in  sample  No.  11  indicates  that  the  rootstock  was  old 
with  meristem  dead,  instead  of  young  and  fresh  as  was  supposed. 

A  number  of  striking  differences,  particularly  with  regard  to  the 
hexoses  of  the  rootstocks,  were  observed  between  hill  3,  3  months 
old,  and  hill  1,  grown  in  an  adjacent  field.  Beginning  with  sample  No. 
12,  the  hexoses  were  about  one-fifth  that  of  the  sucrose.  The 
hexoses  increased  rapidly  and  the  sucrose  decreased  until  in  sample 
No.  15  the  former  exceeded  the  latter.  The  hexoses  of  the  steins 
were  very  low.  The  total  sugars  of  the  Groups  3a  and  3b  rootstocks 
were  unusually  high,  owing  largely  to  their  high  hexose  content, 


2nd       3rd       4th      5th    6th  /st      2nd     3rd     4th 

GE/VE/SslT/O/V  G£N£es4T/0/V 

//  MONTHS  H/LL  3  MONTHS  H/L. 

Fig.  16.— Sugars  in  different  plants  within  the  hill 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE   CANNA       23 

whereas,  the  total  sugars  of  the  stems  were  far  lower  than  those  of  the 
rootstocks,  owing  primarily  to  their  low  hexose  content.  The  very 
low  percentages  both  of  dry  matter  and  of  starch  in  the  rootstock  were 
in  contrast  to  the  hills  previously  mentioned.  The  solids  other  than 
starch  had  practically  the  same  values  as  hills  1  and  2.  The  occur- 
rence of  starch  in  the  stems  has  been  previously  noted  in  a  similar 
bill.     (Table  6,  hill  3.) 

Within  the  stem  the  hexoses  seem  to  be  an  index  of  the  amount 
of  material  being  furnished  to  the  rootstock  for  starch  formation. 
The  sucrose  has  a  more  constant  value  and  shows  less  correlation 
with  the  growth  of  the  hill.  In  the  rootstock,  however,  the  sucrose 
follows  the  variations  of  the  hexoses  of  the  stem  rather  closely  and 
thus  furnishes  a  possible  index  of  the  rate  of  storage  of  starch.  The 
hexoses  remain  low  and  fairly  constant  in  the  mature  rootstock, 
but  increase  in  concentration  in  the  youngest  growth,  and  may  be 
considered  as  an  index  of  the  rate  of  cell  growth  in  the  young 
rootstock. 

It  is  a  significant  fact  that  the  curve  for  the  sucrose  content  of  the 
rootstocks  follows  very  closely  that  of  the  hexoses  of  the  correspond- 
ing stems.  Davis,  Daish,  and  Sawyer  (6)  suggest  that,  in  case  of  the 
sugar  beet,  a  larger  quantity  of  hexoses  is  found  when  the  hexoses 
enter  the  root  in  excess  of  its  "saccharifying  power.'  The  accumu- 
lation of  sucrose  in  the  edible  canna  rootstock  might  be  due  to  its 
production  in  excess  of  its  "amylogenic  power,"  in  which  case  the 
increase  in  the  sucrose  of  the  older  groups  might  be  attributed  to  a 
decrease  in  this  power  rather  than  to  any  increase  in  the  rate  of 
formation  of  starch.  That  starch  formation  was  still  taking  place 
was  shown  by  the  increase  in  the  percentage  of  starch  over  that  of 
preceding  groups.  Evidently  change  from  hexoses  to  sucrose  was 
rapid,  since  in  no  instance  did  the  hexose  content  of  a  Group  2  root- 
stock  show  any  increase,  regardless  of  the  percentage  of  hexoses  in 
the  stem.  The  high  concentration  of  the  hexoses  in  the  stems  of 
Group  2  would  seem  to  indicate  that  this  is  the  stage  in  which  the 
stem  sends  the  largest  quantity  of  sugars  to  the  rootstock.  Sample 
No.  3,  old  Group  2,  had  the  highest  sugar  content  notwithstanding 
the  fact  that  it  had  only  few  green  leaves  at  the  top. 

In  Group  3a,  comprising  immature  stems,  the  sugars  decreased 
sharply.  This  indicates  that  much  of  the  synthesized  plant  foods 
are  carried  to  the  growing  portions  of  the  stem  instead  of  to  the 
rootstock,  and  that  the  stem  does  not  function  at  its  maximum  in 
supplying  sugars  to  the  rootstock  until  all  new  growth  ceases. 

The  hexoses  within  the  rootstock  of  Groups  1,  2,  and  3a  were  uni- 
formly low.  The  slight  effect  on  the  hexoses  of  the  large  variations 
in  the  stems  as  well  as  in  the  sucrose  of  the  rootstocks  in  Groups  2 
and  3a  is  surprising.  Using  the  reducing  sugars  as  a  criterion,  it  is 
seen  that,  in  Groups  2  and  3a,  the  sugars  were  carried  down  the 
stem  at  the  maximum  rate  although  active  cell  growth  of  the  root- 
stock  had  largely  ceased.  This  would  seem  to  indicate  that  the  process 
of  starch  formation  within  the  rootstock  continues  long  after  active 
cell  growth  ceases.  Reference  to  the  starch  content  of  the  different 
groups  tends  to  bear  out  this  observation.  In  sample  No.  6  cell 
growth  was  still  taking  place  since  the  stem  had  not  begun  to  develop 
and  the  apical  growth  was  meristematic.  The  hexoses  were  compar- 
atively high,  whereas  the  starch  content  was  very  low.     The  stem 


24  BULLETIN    56,   HAWAII   EXPERIMENT   STATION 

proper  begins  to  ascend  the  stalk  with  the  development  of  the  first 
leaf,  and  cell  growth  at  the  apex  of  the  rootstock  probably  then 
rapidly  decreases.  In  sample  No.  5,  Group  3a,  the  hexoses  decreased 
to  the  same  level  as  in  the  mature  rootstocks  of  Groups  1  and  2.  The 
starch,  on  the  other  hand,  increased  rapidly,  the  increase  continuing 
through  the  Group  2  stage.8 

A  consideration  of  hill  3  shows  that  the  entire  hill  was  actively 
growing,  the  first  generation  still  being  in  the  Group  3a  stage.  This 
explains  the  low  concentration  of  sugars  in  the  stem.  The  presence 
of  such  large  quantities  of  sugars,  particularly  of  the  hexoses  in  the 
rootstock,  is  noteworthy.  The  very  low  starch  content  in  the  root- 
stocks  and  the  occurrence  of  starch  in  the  stems  leads  to  the  conclu- 
sion that  the  hill  was  still  in  the  process  of  establishment  and  that 
the  rootstock  had  not  begun  to  function  with  sufficient  rapidity  to 
convert  the  sugars  into  starch  as  fast  as  they  were  formed. 

Hill  4,  12  months  old,  from  Waimea,  showed  variations  in  sugar 
very  similar  to  those  of  hills  1  and  2  from  the  station.  The  hexoses 
of  the  stems  were  appreciably  higher  than  in  samples  from  the  sta- 
tion. In  view  of  the  important  part  the  mature  stem  apparently 
plays  in  the  process  of  starch  storage,  it  is  significant  that  the  hill 
had  three  generations  of  stems  all  of  which  functioned  at  nearly  a 
maximum  rate,  whereas  hill  1,  which  was  of  practically  the  same  age, 
had  only  one  generation. 

The  solids  other  than  starch,  representing  the  resultant  of  all  the 
other  variable  constituents,  can  be  interpreted  only  in  a  very  general 
way.  Except  for  the  first  generation  rootstocks,  which  are  essentially 
different  in  structure  from  the  others  in  the  hill,  the  proportions  of 
the  solids  other  than  starch  were  relatively  constant  as  compared 
with  the  corresponding  percentages  of  starch.  Sample  No.  15,  for 
example,  had  only  0.65  per  cent  of  starch,  but  was  less  by  only  1.81 
per  cent  in  solids  other  than  starch  than  sample  No.  2,  which  con- 
tained 25.83  per  cent  of  starch.  This  appears  to  indicate  that  starch 
formation  is  the  principal  change  taking  place  in  the  rootstock 
approaching  maturity. 

A  comparison  of  the  analyses  with  data  previously  published  by 
the  station  (3,  p.  7)  shows  similar  variations,  depending  upon  the 
stage  of  maturity  and  age  of  the  hill.  The  nitrogen-free  extract,  as 
shown  in  the  earlier  literature,  was  appreciably  higher  than  was  the 
proportion  of  starch  in  these  investigations,  because,  in  the  former 
instance,  all  other  carbohydrates  hydrolyzed  by  1.25  per  cent  sul- 
phuric acid  were  included,  whereas  in  this  paper  only  the  true  starch 
as  determined  by  the  diastase  method  is  given. 

VARIATIONS  IN  PLANTS  FROM  IRRIGATED  AND  UNIRRIGATED  HILLS 

Two  adjacent  plats  at  the  station  were  planted  with  canna  and 
irrigated  until  sprouting  occurred.  Irrigation  was  then  discontinued 
on  one  plat,  but  continued  every  fifth  day  on  the  other.  During  the 
hot,  dry  summer  which  followed,  the  unirrigated  plat  produced  a 
very  stunted  crop,  whereas  the  plants  on  the  irrigated  plat  made 


8As  previously  stated  (p.  2),  the  rootstock  continues  to  increase  in  size,  as  was  shown  by  actual 
measurements  in  the  field  and  the  occurrence  of  fresh  cracks  on  the  surface  of  rootstocks  in  old  Groups  3a 
and  2.    The  phenomenon  is  noticeable  particularly  at  Waimea. 


CARBOHYDRATE  METABOLISM  AND  GROWTH   IN  EDIBLE   (ANNA       25 

vigorous  growth.  A  representative  hill  from  each  plat  was  dug  four 
and  one-half  months  after  planting  for  determination  of  sugar.  Table 
8  shows  the  difference  in  the  sugars  of  hills  from  the  two  plat-. 

Table     8. — Sugars    in    4l/2-months-old    canna    plant*    grown    on    irrigated    and 
uuirrigatcd  plats  in  station  field  26 B 

IRRIGATED  PLAT 


6 

Sucrose  in  sap 

Hexoses  in  sap 

Total  sugars  in  sap 

1 

Genera- 
tion 

Stage  of  maturity 

Root- 
stock 

Stem 

Root- 
stock 

Stem 

Root- 
stock 

• 

Stem 

3 
4 

Firs;  .... 
Second 

Young  Group  2 

Old  Group  3a ... 

P(r  cent 
2.91 
2.69 
1.70 
1.44 

Per  cent 

0.51 

.47 

.29 

Per  cent 

0.20 

.33 

.32 

.51 

Per  cent 

0.94 

1.25 

.46 

Per  cent 
3.  11 
3.  02 
2.  02 

,8, 

Per  cent 
1.45 
1.72 

5  Third... 

6  Fourth 

Medium  Group  3a 

Group  3b  (spike) 

.75 

UNIRRIGATED  PLAT 


1  First... 

2  Second. 


Medium  Group  3a 
Young  Group  3a  .. 


1.32 
1.26 


0.37 
.33 


0.26 
.09 


0.31 


1.58 
1.35 


The  sucrose  content  of  the  rootstocks  of  the  irrigated  field  was 
practically  double  that  of  the  unirrigated,  whereas  the  hexoses  were 
not  appreciably  higher  except  for  the  youngest  rootstock.  Likewise, 
the  hexoses  of  the  stems  from  the  irrigated  field  were  much  higher 
than  those  from  the  unirrigated  and  the  percentage  of  sucrose  was 
only  slightly  greater.  In  the  irrigated  field  the  hexoses  of  the  stems 
great!}7  surpassed  the  sucrose,  whereas  the  reverse  was  true  of  the 
unirrigated  field.  The  results  point  strongly  to  the  observations 
previously  noted  that  the  hexoses  of  the  stem  and  the  sucrose  of  the 
rootstock  are  measures  of  the  rate  of  translocation  of  sugars  and 
storage  of  starch. 

EFFECT  OF  IRRIGATING  PLANTS  STUNTED  BY  DROUGHT 

Low  results  were  obtained  in  an  analysis  of  plants  from  a  hill  of 
canna  from  station  field  32C,  which  three  months  previously  showed 
a  high  sugar  content  (see  Table  7,  hill  3),  but  which  had  subsequently 
been  subjected  to  a  hot,  dry  period.  To  determine  whether  the 
severely  stunted  field  would  resume  growth,  with  the  production  of 
good-sized  rootstocks,  a  part  of  the  field  was  irrigated  every  fifth  day 
for  a  period  of  two  months,  when  the  sugars  were  determined  in  plants 
from  both  irrigated  and  unirrigated  parts.  Field  26A,  on  which  the 
plants  had  to  a  considerable  extent  matured  before  the  drought  set  in 
(Table  7,  hill  2),  was  also  included  in  the  study.  Table  9  gives  the 
condensed  results  of  analyses  made  from  time  to  time,  the  average 
composition  of  the  entire  hill  being  given  in  each  instance.  It  fur- 
ther gives,  for  the  sake  of  comparison,  the  average  sugar  content  of  a 
hill  taken  from  each  field  during  the  period  of  optimum  growth. 


26 


BULLETIN   56,   HAWAII   EXPERIMENT   STATION 


Table  9. — Effect  of  irrigation  on  the  sugars  of  stunted  plants 

HILL  NO.  1,  STATION  FIELD  32C  (PLANTED  JAN.  10,  1925) 


Date  of 
harvest 

Period  of 
irrigation ! 

Sucrose  in  sap 

Hexoses  in  sap 

Total  sugars  in  sap 

Specific, 
gravity 

of 
rootstock 

Rootstock 

Stem 

Rootstock 

Stem 

Rootstock 

Stem 

1 

1925 
July  21 

...do 

July  28 
Aug.  14 
Sept.    8 
Apr.     8 

Days 
11 

0 
18 
35 
60 

0 

Per  cent 
0.71 
.56 
.66 
.59 
.60 
1.65 

Per  cent 
0.29 
.31 
.46 
.30 
.29 
.36 

Per  cent 
0.24 
.15 
.29 
.24 
.18 
.72 

Per  cent 
0.43 
.18 
.33 
.51 
.39 
.54 

Per  cent 
0  95 
.71 
.95 
.83 
.78 
2.37 

Per  cent 

0.72 

.49 

.79 
.81 
.68 
.90 

*2 
3 
4 
5 

36 

1.041 
1.053 
1.048 
1.036 
.991 

HILL  NO.  2,  STATION  FIELD  26A  (PLANTED  JAN.  10,  1925) 


7 

July  25 
...do.... 

Aug.  26 
...do.... 

Sept.  2 
...do.... 

Dec.    4 

15 
0 

32 
0 

39 
0 
0 

1.16 
1.16 
2.47 
1.30 
2.83 
1.03 
1.29 

0.08 
.13 
.21 
.19 
.22 
.15 
.21 

1.24 
1.29 
2.68 
1.49 
3.05 
1.18 
1.50 

1.063 

28 

9 

2  10 

11 

212 

.80 
.50 

.58 
.29 

.77 

0.91 
1.20 
.79 
.42 

1.85 

1.71 
1.70 
1.37 
.71 
2.62 

1.068 
1.070 
1.066 

»13 

1.071 

'Irrigation  begun  July  10,  1925. 

2  Unirrigated  portion  of  the  field. 

3  Harvested  at  optimum  growth. 

The  results  show  no  increase  in  the  sugars  in  the  stunted  plants  of 
station  field  32C  after  two  months  of  constant  irrigation.  If  the 
specific  gravity  of  the  rootstocks  is  used  as  an  index  of  their  starch 
content  the  starch  is  seen  to  have  made  no  increase  during  the 
period,  and  the  very  low  hexose  content  of  the  stem  shows  that 
only  a  very  small  quantity  of  sugar  was  being  transported  down  the 
stem.  In  the  unstunted  plants  of  station  field  26A,  however,  not 
only  did  the  sucrose  in  the  rootstocks  increase,  but  the  increase  was 
more  than  double  that  of  the  hill  during  its  optimum  growing  period 
notwithstanding  the  uniformly  low  hexose  content  of  the  stems  and 
the  almost  constant  specific  gravity  of  the  rootstocks.  In  both  plats 
the  new  growth  resulted  in  very  small  rootstocks  and  stunted  stems, 
with  even  the  second  generation  of  renewed  growth  decidedly  under- 
sized. 

The  above  apparent  contradiction  may  be  explained  by  the  fact 
that  the  increase  in  sucrose  in  field  26A  was  in  reality  due  to  break- 
ing down  of  the  starch  previously  stored  in  the  rootstock  to  nourish 
the  buds  developing  on  even  the  oldest  rootstocks  of  the  hill;  whereas, 
in  a  vigorously  growing  hill  the  plant  food  is  supplied  by  the  parent 
stem.  Failure  of  the  sucrose  to  increase  in  case  of  field  32C  may 
have  been  due  to  the  fact  that  the  hill  selected  for  analysis  was 
younger  and  the  developing  buds  were  on  the  youngest  rootstocks 
the  stems  of  which  retained  sufficient  vitality  to  support  a  stunted 
new  growth. 

MATURE  ROOTSTOCKS  DEVOID  OF  STEMS 

Many  old  rootstocks,  the  stems  of  which  always  remain  as  °  spikes/' 
form  a  part  of  every  hill  of  canna.  Failure  to  develop  stems  may 
be  due  to  the  death  of  the  meristem,  as  evinced  by  blackening  of  the 
apex,  or  to  the  increased  vigor  of  the  offspring  which  take  practically 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA       27 

all  the  nutrition  from  the  parent  stem.  In  addition  to  these  old 
rootstocks,  the  hill  contains  the  dormant  rootstocks  (Group  1  stage), 
the  stems  of  which  develop  normally  and  then  die  back.  The  sugars 
of  the  mature  "stemless"  rootstocks  are  of  interest  because  they 
represent  the  residual  components  of  the  rootstocks  unaffected  by 
incoming  materials  from  the  stem. 

Table  10  shows  the  sugar  content  of  a  number  of  rootstocks  which, 
for  one  reason  or  another,  were  devoid  of  stems. 

Table  10. — Sugars  in  sap  of  mature  rootstocks  devoid  of  stems 


Description  of  rootstock 


Sucrose 

Hexoses 

in  sap 

in  sap 

Per  cent 

Per  cent 

1.61 

0.19 

.98 

.22 

2.08 

.22 

1.09 

.00 

2.65 

.15 

.51 

.01 

Total 

sugars  in 

sap 


Dormant;  stem  dead2 

Nonirrigated;  stem  removed  5  months  previous 

Irrigated;  stem  removed  5  months  previous 

Old,  nonirrigated;  spike  dead3 

Old,  irrigated;  spike  dead 

Old,  grown  at  Waimea;  spike  dead 


Per  cent 
1.80 
1.20 
2.30 
1.09 
2.80 
.52 


1  All  samples,  except  No.  6,  were  grown  at  the  station. 

2  Sample  No.  2  of  Table  4. 

3  Attached  to  sample  No.  2. 

The  table  shows  that  sample  No.  1,  the  stem  of  which  developed 
normally  and  subsequently  died,  had  a  comparatively  high  sucrose 
content.  Sample  No.  2,  the  stem  of  which  had  been  removed  while 
still  green,  and  sample  No.  4,  the  spike  of  which  had  died,  showed 
decidedly  lower  concentrations  of  sucrose.  The  increase  of  sucrose 
content  of  samples  Nos.  3  and  5  to  more  than  double  that  of  samples 
Nos.  2  and  4,  respectively,  further  substantiates  the  theory  previously 
advanced  (p.  26)  that  increase  in  sucrose  may  be  due  to  hydrolysis 
of  the  starch  already  formed  in  the  rootstock,  rather  than  to  trans- 
location from  the  stem,  since  the  rootstocks  were  devoid  of  stems. 
Sample  No.  4  was  expected  to  represent  the  minimum  concentration 
of  both  sucrose  and  the  hexoses  possible  within  a  rootstock  because 
it  was  supporting  no  growth  and  was  attached  to  sample  No.  2, 
which  was  without  stem  development.  The  hexose  content  was  nil 
but  the  percentage  of  sucrose  was  not  outstandingly  low,  sample  No. 
6,  which  was  an  old  rootstock  with  dead  spike,  having  less  than  half 
the  quantity. 

An  abnormally  low  sucrose  content  in  a  mature  rootstock  has  been 
frequently  observed  to  accompany  a  low  percentage  of  starch  (deter- 
mined by  the  specific  gravity  method) ,  suggesting  the  possibility  of 
the  sucrose  of  the  rootstock  being  in  some  sort  of  equilibrium  with 
its  starch,  since  a  low  sucrose  content  results  from  a  cell  structure 
"unsaturated"  with  starch,  and  a  high  sucrose  content  from  a  cell 
structure  having  a  high  starch  content.  This  theory  seems  to  be 
confirmed  by  Table  9,  which  shows  that  samples  from  the  unirrigated 
section  of  station  field  26A  had  a  higher  sucrose  content  than  those 
from  station  field  32C,  on  which  the  crop  became  stunted  before  any 
of  the  rootstocks  reached  full  maturitv. 


28 


BULLETIN   56,   HAWAII   EXPERIMENT    STATION 
EFFECT  OF  STORAGE 


Determinations  of  the  sugar  content  of  rootstocks  kept  for  differ- 
ent lengths  of  time  after  digging  in  a  covered  jar  at  room  tempera- 
ture are  given  in  Table  11. 

Table  11. — Effect  of  storage  on  sugar  content  of  sap  of  canna  rootstock 


Age  of 
rootstock 

Time 
stored 

Sucrose 
in  sap 

Hexoses 
in  sap 

Total 
sugars 
in  sap 

Ratio  of 

hexoses  to 

sucrose 

Months 
12 
12 
12 
12 
6 

Days 

........ 

115 
21 
30 

Per  cent 
1.16 
2.62 
3.73 
2.73 
3.06 

Per  cent 

0.13 

.33 

.  55 
.37 

.18 

Per  cent 
1.29 
2.95 
4.28 
3.10 
3.24 

1 
1 
1 
1 
1 

0.112 
0.126 
0.147 
0.135 
0.059 

i  Beginning  to  ferment. 

The  table  shows  that  the  sugars  of  the  stored  rootstock  increased 
continuously  for  about  two  weeks,  when  fermentation  began.  The 
hexose-sucrose  ratio  also  increased.  The  rootstock  which  had  been 
stored  for  21  days  was  decidedly  spongy  and  showed  signs  of  fermen- 
tation. In  this  case  both  forms  of  sugar  decreased  but  the  hexose- 
sucrose  ratio  was  nearly  the  same  as  in  the  rootstock  which  had  been 
stored  for  eight  days.  That  this  did  not  hold  for  all  the  rootstocks 
is  shown  by  the  different  ratio  obtained  in  rootstocks  from  a  6-months- 
old  hill  which  had  given  no  appreciable  sign  of  fermentation  after  it 
had  been  stored  for  30  days.  Unfortunately,  the  original  sugar  con- 
tent of  this  sample  was  not  determined. 

The  results  indicate  the  rapidity  of  the  changes  taking  place  in  the 
canna  rootstock  after  it  is  dug.  Such  changes  would  seem  to  be  of 
considerable  significance  in  extracting  the  starch  for  commercial  uses. 
Although  the  rootstock  can  be  left  in  the  hill  for  a  number  of  months 
after  maturity  without  deteriorating,  its  value  for  starch  manufac- 
ture is  greatly  impaired  by  a  few  days'  exposure  after  digging.  The 
starch  granules  remain  unaffected  for  some  time,  but  purification  and 
sedimentation  are  rendered  difficult  by  the  large  amount  of  slimy 
precipitate  which  settles  out  even  before  the  rootstock  shows  sign  of 
fermentation  or  decay. 

DORMANT  AND  ACTIVELY  GROWING  PLANTS 

At  Waimea  a  field  of  canna  developed  neither  new  steins  nor  rooi- 
stocks  during  a  period  of  about  three  months.  However,  the  stems 
already  developed  were  protected  from  injury  by  continuous  mists 
and  by  windbreaks.  Toward  the  end  of  the  dormant  period  a  hill  was 
dug  for  sugar  determination.  Two  months  later  the  field  showed  vig- 
orous development  of  both  new  stems  and  rootstocks.  Another  hill 
was  then  dug  from  the  same  section  as  the  first.  Table  1 2  compares  the 
sugar  content  of  the  two  hills. 


CARBOHYDRATE  METABOLISM  AND  GROWTH   IN  EDIBLE   CANNA       29 


Table  12. — Differences  in  the  sugars  in  sap  of  dormant  and  actively  growing  -plank 
(DORMANT)  HILL  NO.  1,  13  MONTHS  OLD,  WAIMEA  FIELD  A 


Genera- 
tion 

Stage  of  maturity 

Sucrose  in  sap 

Hexoses  in  sap 

Total  sugars  in  sap 

2  G 

■sa 

"   C3 

Root- 
stock 

Stem 

i 

Root- 
stock 

Stem 

1 

First. 

Old  Group  2 

Per  cent 
0.96 
.76 
.79 
.82 
.51 
.99 

Pereent 
0.64 
.58 

i 

Percent     Ptrcent 

0. 18            1.  25 

.13              1.53 

Per  cent 
1.14 
.89 
.84 
1.06 
.52 
1.23 

Per  cent 
1  89 

2  Second  . 

3  Third... 

4  Fourth  . 

Medium  Group  2 

2. 11 

do 

.  91              .  05            1. 70 
.41 

2  61 

Young  Group  2. 

2  59 

5     ...do 

Old;  spike,  dead. 

•01    

.24               .87 

6 

Old  Group  3a 

.35 

1  22 

(ACTIVELY  GROWING)  HILL  NO.  2,  15  MONTHS  OLD,  WAIMEA  FIELD  A 


7  Third. .. 

8  Fourth . 

9  Fifth  ... 

10  Sixth  ... 

11  Seventh. 


Medium  Group2. 

Old  Group  3a 

do 

Young  Group  3a. 
Group  3b  (spike) 


1.82 

1.34 

0.19 

3.41 

2.01 

.90 

1.01 

.09 

2.48 

.99 

1.03 

.90 

.14 

2.31 

1.17 

1.51 

.26 

.33 

.83 

1.84 

1.46 

.64 

2.10 

4.75 
3.49 
3.21 
1.09 


'Sample  No.  7,  third  generation,  hill  2,  is  comparable  with  sample  No.  3,  hill  1,  since  the  first  and 
second  generations  were  not  included  in  the  analysis  of  hill  2. 

The  dormant  canna  (fig.  17)  wTas  conspicuous  by  the  abnormally  low 
sucrose  content  of  its  rootstocks.  The  hexoses  of  the  stems  were  also 
considerably  below  those  previously  noted  in  canna  grown  at  Waimea. 
(Table  7,  hill  4.) 

Both  the  hexoses  and  the  sucrose  were  greater  in  old  stems  of  the 
vigorously  growing  canna  than  in  the  dormant  canna.  Although  in 
sample  No.  7,  third  generation  of  the  actively  growing  canna,  the 
sucrose  increased,  in  samples  8  and  9  of  the  fourth  and  fifth  genera- 
tions, respectively,  it  showed  little  increase  over  samples  Nos.  4  and 
6  of  the  corresponding  generations  of  the  dormant  canna,  notwith- 
standing the  increase  in  sugars  in  the  stems.  However,  the  sugars 
in  the  rootstocks  of  the  sixth  and  seventh  generations  of  the  actively 
growing  canna,  representing  the  new  growth,  were  rather  normal  for 
Groups  3a  and  3b  stages  of  development. 

These  results  confirm  observations  previously  made  (p.  26)  that 
usually  when  sugars  within  a  rootstock  decrease  to  a  low  level  for  a 
prolonged  period  they  do  not  again  increase  unless  hydrolysis  of 
starch  occurs.  Whether  this  indicates  a  loss  in  amylogenic  power  in 
such  rootstocks  is  not  certain.  That  this  is  sometimes  the  case  would 
seem  to  be  indicated  by  the  very  low  starch  content  frequently  ob- 
served in  rootstocks  in  the  dormant  stage,  Group  1 .  The  recovery 
of  the  Waimea  field  from  a  dormant  period  with  subsequent  produc- 
tion of  good-sized  rootstocks  in  its  new  growth,  in  striking  contrast 
with  the  severe  stunting  of  the  new-  growth  at  the  station,  may  be 
attributed  to  the  unaffected  condition  of  the  stem  growTth,  which  con- 
tinued to  function,  whereas  at  the  station  it  was  practically  de- 
stroyed. 


30 


BULLETIN   56,   HAWAII   EXPERIMENT   STATION 


CRYOSCOPIC   MEASUREMENTS  AND   OSMOTIC    PRESSURE   OF   THE 

PLANT  JUICES 

The  method  of  measuring  osmotic  pressure  of  expressed  saps  based 
on  freezing-point  depression  has  been  extensively  used  in  studying 
the  growth  of  plants,  their  adaptability  to  different  environments, 


5.00 


400 


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GOOrSTOCA 


2nd 


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3rd        4th        5th 


HEXOSES 


STE*- 


2nd       3rd        4th 


5th 


TOZ4L  SUG42& 


/st 


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TsT 


2nd 


2nd 


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3rd        4th 


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5th        6th 


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3rd       4th       5th 


6th 


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GEME£>4T/ON 

DOA7M^A/T  PEa?/OD 
/3  MONTHS  OLD 


GEA/Ea9>7T/OA/ 

^/CT/^ELV  G20W/A/C  P£a?/OD 
S/fME  F/ELD  2  MONTHS  L/JTEG 


Fig.  17.— Sugars  in  a  field  of  carina  during  a  dormant  and  an  actively  growing  period 

and  the  movement  of  plant  fluids  in  different  parts  of  the  organism. 
To  learn  whether  results  obtained  by  this  method  would  substantiate 
the  conclusions  drawn  from  the  preceding  study  of  the  sugars  in  the 
plant  sap,  determinations  were  made  of  the  osmotic  pressures  of  the 
tissue  fluids  from  the  rootstocks,  stems,  and  leaves  of  canna  plants, 
using  cryoscopic  measurements,  as  outlined  by  Harris  and  Gortner 


CARBOHYDRATE  METABOLISM  AND  GROWTH  IN  EDIBLE  CANNA       31 

(7).9     Determinations  were  made  in  duplicate  in  the  rootstock  and 
stem  samples.     The  results  are  given  in  Table  13. 

Table  13. — Osmotic  pressure  and  freezing-point  depression  of  sap  from  the  canna 

plant 


Rootstocks 

Stems 

Leaves 

Stage  of  maturity 

Depression 

of  the 

freezing 

point 

Osmotic 
pressure 

Depression 

of  the 

freezing 

point 

Osmotic 
pressure 

Depression 

of  the 

freezing 

point 

Osmotic 
pressure 

{ 

°C. 
0.789 
.797 

Atmosphere 
9.502 
9.599 

°C. 

Atmosphere 

°C. 

Atmosphere 

Average 

.793 

9.551 

{ 

.810 
.833 

9.  755 
10.  933 

0.763 
.753 

9.190 
9.069 

Average 

.822 

10.  344 

.758 

9.129 

Group3a 

{ 

.726 

.785 

8.745 
9.454 

.804 
.821 

9.683 
9.887 

Average 

.756 

9.099 

.813 

9.785 

0.683 

8.227 

{ 

.772 
.781 

9.298 
9.406 

.614 
.694 

7.  397 
8.360 

Average 

.777 

9.  352 

.654 

7.879 

.592 

7  132 

The  results  given  in  Table  13  are  not  sufficient  to  warrant  definite 
conclusions.  However,  the  close  agreement  of  the  results  with  the 
variations  in  the  sugar  content  of  similar  samples  is  worthy  of  note. 

The  osmotic  pressure  reached  its  maximum  in  the  rootstocks  of 
Group  2  and  diminished  through  Groups  3a  and  3b,  which  also  was 
true  of  the  sucrose.  Since  usually  the  hexoses  in  the  rootstocks  were 
negligible,  the  total  sugars  showed  the  same  variation.  The  osmotic 
pressure  in  the  stem  reached  its  maximum  in  Group  3a,  whereas  the 
sugars  were  greatest  in  Group  2.  However,  the  rise  and  subsequent 
decrease  of  the  hexoses  and  total  sugars  in  progressing  from  Group  1 
to  Group  3b  were  apparent  in  the  osmotic  pressure.  Moreover,  the 
differences  in  the  depression  of  the  freezing  points  of  the  rootstocks, 
expressed  in  terms  of  sucrose,  were  practically  the  same  as  the  differ- 
ences in  the  total  sugars  of  the  rootstocks  given  in  Table  7.  The 
same  was  true  of  the  hexoses  of  the  stems.  The  difference  in  the 
average  depression  of  the  freezing  point  of  the  rootstock  of  Groups 
2  and  3b,  for  example,  was  0.45°  C,  which  is  equivalent  to  0.83  per 
cent  sucrose,  whereas  the  difference  in  the  total  sugars  of  Groups  2 
and  3b  (samples  Nos.  3  and  6,  Table  7),  was  1.01  per  cent.  Although 
exact  figures  have  no  significance  in  this  connection,  since  the  freez- 
ing point  and  the  sugar  determinations  were  made  on  different  samples 
representing  the  same  group  of  rootstocks,  the  comparisons  are  worthy 

•The  determinations  were  made  at  the  station  in  1924  by  Charles  C.  Crane,  under  the  direction  of 
J.  A.  Harris,  department  of  botany.  University  of  Minnesota.  Doctors  Harris  and  R.  A.  Oortner,  also 
of  the  University  of  Minnesota,  used  the  chemical  laboratory  facilities  of  the  station  in  obtaining  cryo- 
scopic  and  conductivity  data  on  Hawaiian  plants,  in  exchange  for  which  courtesy  they  collected  the  canna 
samples  and  turned  over  to  the  station  the  data  accumulated. 


32  BULLETIN   56,   HAWAII   EXPERIMENT   STATION 

of  consideration.  The  leaves  had  the  lowest  osmotic  pressure  of  any 
of  the  different  parts  of  the  plant.  Reference  to  Table  7  shows  that 
this  was  also  true  of  the  total  sugars. 

DISCUSSION  OF  RESULTS 

The  results  obtained  in  this  investigation  lead  to  a  number  of 
practical  conclusions.  That  the  stem  of  the  canna  plant  functions 
strongly  in  influencing  the  size  of  the  offspring  was  confirmed  by 
these  results,  which  point,  moreover,  to  the  importance  of  the 
mature  stem  in  storing  starch  within  its  own  rootstock.  The  starch 
content  of  the  rootstock  is  lowered  when  normal  dying  back  of  the 
leaves  of  the  mature  stem  is  unduly  hastened  by  unfavorable  weather. 
The  fact  that  the  immature  stem  fails  to  contribute  much  plant  food 
to  the  rootstock  and  the  mature  stem  continues  to  function  at  its 
maximum  until  it  is  well  along  in  the  mature  stage  emphasizes  the 
importance  of  prolonging  the  life  of  the  latter  group. 

A  comparison  of  stem  growth  at  the  station  and  in  Waimea  shows 
that  at  the  station  the  stem  maintains  its  maximum  rate  of  sugar 
production  for  a  short  time  only,  whereas  in  Waimea  it  persists  for 
a  much  longer  period.  Although  the  loose,  loamy  soil  of  Waimea  is 
probably  better  adapted  to  a  root  crop  than  are  the  heavy  soils  of 
the  station,  the  climate,  which  prolongs  the  life  of  the  mature  stem, 
is  especially  favorable  to  the  crop.  The  use  of  such  artificial  aids  as 
windbreaks  to  protect  the  stem  from  damage  would  seem  to  be  war- 
ranted. 

The  significance  of  the  stem  in  maintaining  the  new  growth  of  the 
hill  is  also  brought  out.  Attempts  at  the  station  to  renew  growth 
on  fields  where  the  stems  had  been  severely  checked  by  drought  re- 
sulted in  a  small  crop  of  extremely  stunted  character,  whereas  at 
Waimea,  where  the  stem  growth  had  persisted  through  a  long,  dor- 
mant period,  the  new  growth  produced  fairly  good-sized  rootstocks. 

Usually,  the  starch  content  of  a  rootstock  of  the  immature  stage 
is  low  and  steadily  increases  until  the  rootstock  is  well  along  in  the 
mature  stage.  This  fact  would  seem  to  warrant  carefully  surveying 
the  field  before  harvesting,  which  is  ordinarily  done  at  a  definite  age, 
say,  15  months.  If  a  large  part  of  the  growth  is  in  the  immature 
stage,  the  crop  should  be  allowed  to  grow  for  an  additional  period 
so  as  to  increase  the  starch  content  of  the  young  rootstocks.  On  the 
other  hand,  when  a  dormant  period  prevents  new  rootstocks  from 
forming  at,  say,  14  months,  nearly  all  the  rootstocks  will  be  in  the 
mature  stage,  and  the  crop  may  as  well  be  harvested  at  once  because 
the  new  rootstocks  will  not  attain  any  appreciable  starch  content  for 
several  additional  months.  Inability  of  the  crop  to  make  renewed 
growth  with  the  production  of  rootstocks  of  fairly  good  size  after  the 
top  growth  has  been  destroyed  would  seem  to  be  sufficient  reason  for 
harvesting,  regardless  of  the  age  of  the  crop.  Since,  under  normal 
conditions,  a  field  of  canna  is  irregularly  but  continuously  growing, 
it  can  never  be  definitely  stated  when  the  entire  hill  is  mature,  and 
a  criterion  other  than  age  should  be  used  to  determine  the  best  time 
to  harvest. 

Not  only  should  the  classification  of  the  growth  of  a  field  be  deter- 
mined before  harvesting  but  the  approximate  starch  content  of  the 


CARBOHYDRATE   METABOLISM  AND  GROWTH  IN  EDIBLE   (ANNA       33 

crop  also  should  be  ascertained  by  its  specific  gravity.  A  simple 
method  consists  in  weighing  a  lot,  say,  50  pounds,  of  cleansed  root- 
stocks  in  a  wire  basket,  first  in  air  and  then  immersed  in  kerosene. 
The  starch  content  can  then  be  ascertained  by  referring  to  Table  5, 
page  11. 

SUMMARY 

In  this  series  of  experiments,  made  to  study  continuously  the 
growth  of  edible  canna  {Carina  edulis)  and  the  occurrence  of  sugars 
and  their  changes  during  translocation  and  ultimate  storage  as  starch 
in  the  plant,  it  was  found  that  sucrose  is  the  chief  sugar  of  the  leaves; 
the  hexoses  are  present  in  only  very  small  quantities,  and  the  hexose- 
sucrose  ratio  is  always  very  low.  This  is  true  of  leaves  from  an  old 
mature  plant  as  well  as  from  a  young,  rapidly  growing  plant.  The 
percentage  of  sucrose  is  lower  in  the  midribs  and  the  sheaths  than  in 
the  leaves,  whereas  that  of  the  hexoses  is  much  higher.  In  the  stem 
proper  the  hexoses  are  present  greatly  in  excess  of^the  sucrose. 

The  sucrose  in  the  apical  part  of  the  rootstock,  as  compared  with  the 
stem,  increases  and  the  hexoses  correspondingly  decrease.  In  the 
basal  part  of  the  rootstock  both  sugars  usually  decrease,  especially 
the  hexoses,  which  reach  a  very  low  percentage.  The  hexoses  are 
therefore  thought  to  be  the  chief  sugars  of  translocation  and  the 
starch  in  the  rootstocks  to  be  formed  from  sucrose  rather  than  from 
the  hexoses. 

A  study  of  plants  of  different  stages  of  maturity  shows  that  the 
quantity  of  hexoses  is  much  less  in  the  immature  stems  than  in 
the  mature  stem,  owing  to  the  diversion  of  the  flow  in  the  former  to 
the  apical  growth  of  the  plant.  This  indicates  the  value  of  the 
mature  stem  in  the  synthesis  of  food  material.  The  sucrose  content 
of  the  rootstocks  shows  a  similar  variation  to  the  hexoses  of  the  stem, 
the  immature  rootstocks  having  a  much  lower  percentage  of  sucrose 
than  the  mature  ones. 

Young  and  vigorously  growing  rootstocks  are  characterized  by  a 
high  percentage  of  the  hexoses  which  occasionally  exceed  the  sucrose. 
In  the  more  mature  rootstocks  the  hexoses  are  consistently  low  in 
quantity  indicating  their  association  with  the  growing  parts  of  the 
rootstock.  The  concentrations  of  the  hexoses  in  the  stem  and  of 
sucrose  in  the  rootstock  would  seem  to  be  good  indicators  of  the 
rate  of  transposition  of  sugars  and  their  ultimate  storage  as  starch 
in  the  rootstock.  The  sucrose  of  the  stem  and  the  hexoses  of  the 
rootstock  are  usually  more  constant  and  do  not  seem  to  correlate  so 
well  with  growth,  as  determined  by  observations. 

The  sucrose  content  of  the  rootstock,  especially  one  that  is  imma- 
ture, is  lowered  when  normal  growth  is  halted  for  a  protracted  period. 
A  return  of  favorable  growing  conditions  often  fails  to  cause  any 
increase  in  the  sucrose  content.  This  fact,  together  with  the  low 
starch  content  of  the  rootstock,  indicates  a  loss  of  amylogenic 
power. 

Copious  irrigation  of  a  field  of  stunted  plants  may  result  in  an 
increase  of  sucrose  in  the  rootstock,  but  the  increase  seems  to  be  due 
to  the  process  of  "germination,"  or  hydrolysis  of  the  starch  already 
stored  in  the  rootstock  to  support  secondary  growth  development. 


34  BULLETIN    56,   HAWAII   EXPERIMENT   STATION 

In  the  mature  rootstock  the  sucrose  content  varies  greatly  under 
different  conditions.  Indications  are  that  it  exists  in  some  sort  of 
equilibrium  with  the  starch,  since  the  sucrose  content  is  low  in  root- 
stocks  having  a  low  starch  content  and  high  in  those  having  a  high 
starch  content. 

When  stem  growth  has  not  been  injured  during  the  dormant 
period,  new  growth  with  rootstocks  of  fairly  good  size  is  produced, 
whereas  stunted  stems  produce  extremely  stunted  rootstocks. 

The  percentage  of  starch  varies  widely  in  canna  rootstocks  of  dif- 
ferent stages  of  maturity.  Starting  with  a  low  content  in  the  very 
young  rootstock,  the  starch  increases  up  to  the  dormant  stage  of  the 
rootstock,  the  increase  being  accompanied  by  an  increase  in  specific 
gravity.  Graphs  of  the  starch  show  that  although  the  "  growth 
curve "  of  different  hills  varies  somewhat  the  correlation  between 
specific  gravity  and  the  percentage  of  starch  is  general.  A  table  has 
been  constructed  (Table  5,  p.  11),  which  makes  it  possible  to  deter- 
mine in  the  field  or  the  factory  the  approximate  percentage  of  starch 
in  a  rootstock  from  its  specific  gravity. 

Determinations  of  osmotic  pressures  by  cryoscopic  measurements 
were  made  with  a  limited  number  of  plants.  The  results  confirm 
the  general  conclusions  regarding  growth  drawn  from  the  study  of 
the  carbohydrate  metabolism  of  the  plant. 

LITERATURE  CITED 

(1)  Association  of  Official  Agricultural  Chemists. 

1920.  official  and  tentative  methods  of  analysis.     as  compiled  by 

the  committee  on  revision  of  methods.     revised  to  nov.  1, 
1919.     417  p.,  illus.     Washington,  D.  C. 

(2)  Brown,  H.  T.,  and  Morris,  G.  H. 

1893.    A  CONTRIBUTION  TO  THE  CHEMISTRY   AND    PHYSIOLOGY    OF   FOLIAGE 

leaves.     Jour.  Chem.  Soc.  [London]  63  :  604-677. 

(3)  Chung,  H.  L.,  and  Ripperton,  J.  C. 

1924.  edible  canna  in  Hawaii.  Hawaii  Agr.  Expt.  Sta.  Bui.  54,  16  p., 
illus. 

(4)  Colin,  H. 

1914.    SUR  LA  SACCHAROGENIE  DANS  LA  BETTERAVE.       Compt.  Rend.  Acad. 

Sci.  [Paris]  159  :  687-689. 

(5)  Davis,  W.  A.,  and  Sawyer,  G.  C. 

1916.  STUDIES  OF  THE  FORMATION  AND  TRANSLOCATION  OF  CARBOHY- 
DRATES IN  PLANTS.  III.  THE  CARBOHYDRATES  OF  THE  LEAF  AND 
LEAF  STALKS  OF  THE  POTATO.  THE  MECHANISM  OF  THE  DEGRA- 
DATION of  starch  in  the  leaf.  Jour.  Agr.  Sci.  [England] 
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leaf.     Jour.  Agr.  Sci.  [England]  7:255-326,  illus. 

(7)  Harris,  J.  A.,  and  Gortner,  R.  A. 

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(9)  Lutman,  B.  F. 

1919.    OSMOTIC    PRESSURES  IN   THE  POTATO  PLANT  AT  VARIOUS  STAGES   OF 

growth.     Amer.  Jour.  Bot.  6:181-202,  illus. 

(10)  Meyer,  A. 

1885.  UEBER  die  ASSIMILATIONSPRODUCTE  der  laubblatter  angio- 
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457,  465-472,  481-491,  497-507,  illus. 


CARBOHYDRATE  METABOLISM   AND  GROWTH  IN  EDIBLE  CANNA       35 

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1862.  UEBER  DEN  EINFLUSS  DES  LICHTES  AUF  DIE  BILDUNG   DES    AMYLUM8 
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(13)  ScHIMPER,   A.   F.   W. 

1885.     UEBER    BILDUNG    UND    WANDERUNG    DSB     K  <  )II  LKHYDRATE    IN    DEN 

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1907.   EIN     BEITRAG     ZUR   KENNTNIS    DES    KOHLENHYDRATSTOFFWECHSELS 

von     beta     vulgaris    (zuckerrube).     Sitzber,    Akad.    Wiss. 
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Chim.  Sucr.  et  Distill.  31  :  164-172.      (Discussion  by  A.  Vivien 
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(16)  Wiley,  H.  W, 

1914.  principles  and  practice  of  agricultural  analysis.     Ed.  2,  rev. 

and  enl.,  v.  3,  illus.     Easton,  Pa.,  and  London,  England. 


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